[top]
000
FXUS65 KBYZ 192121
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
321 PM MDT SUN MAY 19 2013
.SHORT TERM...VALID FOR MON AND TUE...
NEGATIVE TILTED TROUGH WILL REMAIN OVER THE AREA TONIGHT AND
CONTINUE TO BRING PERIODS OF MODERATE TO HEAVY RAIN FALL TO
PORTIONS OF SOUTH CENTRAL AND SOUTH EAST MONTANA.
TONIGHT THROUGH TUESDAY NIGHT...MODELS HAVE COME INTO BETTER
AGREEMENT WITH THE 12Z RUN AS THE GFS/ECMWF ARE CLOSING OF AN
UPPER LOW WITH THE TROUGH OVER THE WESTERN DAKOTA`S. THE 500 AND
700 MB LOWS ARE NEARLY STACKED AND THIS WILL ALLOW MORE RAIN TO BE
WRAPPED BACK INTO OUR AREA OVERNIGHT. HEAVY RAIN WILL FALL FROM
LIVINGSTON TO BILLINGS THROUGH THE EVENING DUE TO STRONG FORCING
WITH THE TROUGH AND DEEP UPSLOPE FLOW FROM THE SURFACE TO 20
THOUSAND FEET. THE FORCING WILL SHIFT SLOWLY EAST OVERNIGHT AND
WE WILL BEGIN TO SEE A DECREASE IN PRECIPITATION COVERAGE FROM
WEST TO EAST. THE EAST WILL CONTINUE TO SEE PRECIPITATION MONDAY
THROUGH TUESDAY AS THE UPPER LOW WOBBLES OVER THE DAKOTA`S. THE
UPPER LOW WILL BE KICKED EASTWARD ON TUESDAY AS ANOTHER DEEP
TROUGH OF LOW PRESSURE MOVES ONTO THE WEST COAST. THIS WILL BRING
WEAK SHORT WAVE RIDGING ON TUESDAY WITH MOST OF THE AREA REMAINING
DRY. A FEW SHOWERS WILL LINGER OVER SOUTHEAST MONTANA ON TUESDAY
BUT WILL BE ENDING BY EVENING. TEMPERATURES WILL REMAIN BELOW
NORMAL ON MONDAY BUT ARE EXPECTED TO RETURN TO SEASONAL VALUES ON
TUESDAY.
THE AMOUNT OF DYNAMICS THIS TROUGH HAS GENERATED THE PAST THREE
DAYS HAS BEEN IMPRESSIVE WITH THE ENTIRE FORECAST AREA RECEIVING
FROM 1/2 INCH TO OVER 3 INCHES OF PRECIPITATION. RICHMOND
.LONG TERM...VALID FOR WED...THU...FRI...SAT...SUN...
OVERALL EXTENDED FORECAST IN GOOD SHAPE...WITH A SLOWER
PROGRESSION TO DRY WEATHER THAN PREVIOUSLY ADVERTISED. MODELS
ARE IN PRETTY GOOD AGREEMENT...SLOW TO MOVE CURRENT SYSTEM
EAST...AND SUPPRESSING RIDGE DEVELOPMENT IN BETWEEN AT THIS TIME
AS THE PACIFIC LOW PUSHES EASTWARD. THE EXTENDED FORECAST PERIOD
APPEARS RELATIVELY UNSETTLED OVERALL...ALTHOUGH MARKEDLY DRIER
THAN THE CURRENT WEATHER ACROSS THE REGION. TEMPS THROUGH THE
PERIOD ARE EXPECTED TO BE AROUND SEASONAL AVERAGE...WITH ONLY A
FEW DEGREES ABOVE OR BELOW.
PRECIP FROM DEPARTING SYSTEM STILL APPEARS TO LINGER IN EXTREME
EASTERN MONTANA ON WEDNESDAY...WITH THE TROF SLOW TO MOVE
EASTWARD. SOUTHWEST FLOW ALOFT SETS UP ACROSS THE REGION AS THE
STRONG UPPER LEVEL PACIFIC LOW CONTINUES PUSH EASTWARD...AND SENDS
A STRONG SHORTWAVE THROUGH THE REGION WEDNESDAY. THIS WAVE
APPEARS THAT IT WILL MAINLY IMPACT THE HIGH TERRAIN AND WESTERN
PLAINS...BUT PRECIP WILL ALSO BE POSSIBLE ACROSS THE EAST.
MEANWHILE LOW LEVEL EASTERLY FLOW APPEARS TO SET UP ACROSS THE
REGION...BRINGING MORE LOW LEVEL MOISTURE INTO THE AREA. THE UPPER
LEVEL LOW REMAINS CENTERED OVER WASHINGTON THROUGH
FRIDAY...MAINTAINING UNSETTLED SOUTHWEST FLOW ACROSS THE AREA.
THE LOW FINALLY KICKS NORTHEAST FRIDAY NIGHT...TAKING MOST ENERGY
NORTH OF THE CWA...BUT SOUTHWEST FLOW ALOFT IN PLACE...WITH
POSSIBLE GULF SFC MOISTURE INFLUX THROUGH THE REMAINDER OF THE
PERIOD. AT LEAST SLIGHT POPS CANNOT BE RULED OUT THROUGHOUT THE
REMAINDER OF THE PERIOD...IF ONLY DUE TO DIURNAL HEATING AND
AVAILABLE SURFACE MOISTURE...NOT TO MENTION POTENTIAL WEAK
SHORTWAVES THROUGH THE SOUTHWEST FLOW. AAG
&&
.AVIATION...
WIDESPREAD SHOWERS WILL CONTINUE ACROSS MUCH OF THE REGION TONIGHT
WITH AREAS OF MVFR TO IFR CONDITIONS EXPECTED. MOUNTAINS WILL BE
OBSCURED INTO MONDAY. AAG
&&
.PRELIMINARY POINT TEMP/POPS...
MON TUE WED THU FRI SAT SUN
-----------------------------------------------------------
BIL 049/061 044/069 046/069 049/072 049/074 050/075 050/074
+8/W 41/B 02/T 42/T 22/T 22/T 22/T
LVM 046/059 038/065 040/067 040/067 041/069 042/069 041/068
86/W 41/B 14/T 44/T 43/T 33/T 32/T
HDN 050/061 045/070 044/071 049/074 048/077 050/077 050/076
++/W 51/B 02/T 32/T 22/T 22/T 22/T
MLS 051/059 046/064 046/068 050/071 050/074 052/076 053/076
++/W 73/W 12/T 22/T 22/T 22/T 22/T
4BQ 048/056 044/062 044/068 048/072 049/074 051/076 052/077
++/W 74/W 22/T 22/T 22/T 22/T 22/T
BHK 047/056 042/058 044/064 047/067 048/070 051/074 052/073
++/W 84/W 22/T 22/T 22/T 22/T 22/T
SHR 046/056 041/062 040/069 046/072 046/075 048/075 048/074
++/W 52/W 12/T 32/T 22/T 22/T 22/T
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...FLASH FLOOD WATCH IN EFFECT THROUGH LATE MONDAY NIGHT FOR
ZONES 29>31-36>38-57-58.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
[top]
000
FXUS65 KMSO 192035
AFDMSO
Area Forecast Discussion
National Weather Service Missoula MT
235 PM MDT Sun May 19 2013
.DISCUSSION...Rain-showers have begun to develop across western
Montana this afternoon and is expected to increase in coverage
early this evening. There is also a slight chance for an isolated
thunderstorm to develop in northwestern Montana, mainly in Lake
and Flathead Counties. There is some good news for the near term
forecast with the return to warmer and drier conditions. High
temperatures for Monday and Tuesday will once again be back in the
mid 70`s with mostly sunny skies.
Most significant change to the forecast for Wednesday and beyond
was an increase in temperatures for Wednesday and Thursday morning
with a continued model trend to slow the system down and warm it
up. While snow at mountain passes is possible, recent trends
suggest most of the precipitation will fall overnight as rain.
Northwestern Montana from Troy through Glacier National Park will
receive the most rain with around half an inch expected for most
locations. Main impacts include swollen streams and potential for
mountain snow to affect travel over passes Thursday morning,
especially Marias pass. Impacts in central Idaho and southwestern
Montana will be mediocre in terms of precipitation and snow.
Beyond Wednesday, forecast model agreement is increasing to keep
the low pressure system lingering over the northwest. Expect
slightly cooler than average temperatures during the day and
periods of rain lasting several hours at a time. Those planning
outdoor activities for Memorial Day weekend should be prepared for
wet weather.
&&
.AVIATION...Rain-showers will once again develop across western
Montana and central Idaho this afternoon that could temporarily
reduce visibility and lower ceilings. Clouds will also obscure
mountain tops around all aviation sites. A few isolated
thunderstorms are also possible this afternoon, mainly for
northwestern Montana. Gusty northwest winds will also impact
aviation terminals till after 20/0400Z. KGPI will see gusty winds
out of the southeast, till after 20/0400Z.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&
$$
Follow us on Facebook and Twitter!
https://www.facebook.com/US.NationalWeatherService.Missoula.gov
https://www.twitter.com/NWSMissoula
[top]
000
FXUS65 KTFX 192035
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
235 PM MDT Sun May 19 2013
.DISCUSSION...
Tonight through Tuesday...A snow moving upper level trough over
the Pacific Northwest continues to slowly progress eastward. A
deep low center over the Dakotas continues to wrap good amounts of
moisture into central Montana. The models are in pretty good
agreement as to the placement of the weather patterns in the short
term. This pattern will continue the showery pattern of the past
couple of days. Some greater instability across north central
Montana has enhanced the probability of thunderstorms in this
area. These thunderstorms will bring locally heavier downpours,
and even some small hail late this afternoon and evening. Showers
will diminish somewhat on Monday as the upper low continues its
eastward slide. However, showers will continue along the Rocky
Mountain Front and southward towards the Little Belts. Amounts
will be lighter on Monday. Overnight Monday and into Tuesday,
drying will take place as a weak upper level ridge builds into
central Montana. Temperatures will be warmer Tuesday with the
drier air. db
Tuesday Night through Sunday...Only slight changes noted in forecast
model solutions from previous runs for this period. Two elements, a
ridge of high pressure centered in Saskatchewan extending into the
Upper Midwest states and a closed upper level low pressure system
over the PacNW will be the main weather features for our region.
Neither feature moves much until late next weekend, leaving us in a
persistent pattern of mild and moist southerly flow that will
produce partly to mostly cloudy skies with a chance of light rain
almost every day. Timing for the precipitation remains a bit elusive
at this point, as models continue to show the PacNW system making a
big, slow loop from the Pacific coast thru WA/OR then back into
BC/Alb. Shortwave trofs spinning off the main low center generally
stay along/west of the Continental Divide, but pronounced east-
southeast flow at the low- and mid-levels east of the Divide is
expected to pull moisture around the base of the Canadian high and
across MT, leading to upslope (cloudy) conditions and the
aforementioned periods of light rain. The one notable difference
from the earlier model runs is that both the GFS and ECMWF now push
a cool front thru our region on Friday. The front will be
accompanied by a negatively-tilted (oriented NW-SE) trof and a
possibly some jet stream effects, which typically leads to better
chances of thunderstorms and higher rainfall amounts, which the
models are indeed suggesting at this point. Will keep an eye on how
the models handle the evolution of the Friday conditions,
particularly for the precipitation totals and what effect that will
have on our local streams/rivers. The overall pattern begins to
modify on Sunday with the Canadian high pushing east and the PacNW
low weakening and also tracking east along the US/Can border,
setting up a more typical westerly flow regime. Lastly, expect high
temperatures to remain close to normal (mid 60s) each day this week.
Waranauskas
&&
.AVIATION...
UPDATED 1800Z.
Slight instability and widespread moisture will
keep skies BKN-OVC across southwest and central MT with mix of
VFR/MVFR ceilings today. Scattered showers expected near all TAF
sites through the day with occasional periods of light rain.
Ceilings may briefly drop to IFR category while precipitation is
occurring. There is also a slight chance for a few short-lived
thunderstorms to develop this aftn, but probabilities currently
too low to mention in latest TAFs. Light winds expected today.
Waranauskas
&&
.HYDROLOGY...
First of two slow moving upper level low pressure systems will
bring widespread showers to much of north central and SW MT
through Monday with the second upper level low moving to a position
over the Pacific NW Wednesday and remaining nearly stationary into
next weekend bringing additional precipitation to the region. Cooler
temperatures have reduced snowmelt from higher elevations, however
there are still concerns that rain on the melting snowpack may cause
enhanced rises in stream/river levels in some areas. Most area
rivers are currently well below flood stage but some smaller
tributaries are likely near or approaching bankfull, so rainfall
totals and river stage forecasts will be closely monitored for
significant changes and impacts. Hoenisch
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 44 64 42 72 / 70 60 20 10
CTB 43 64 42 71 / 70 50 20 10
HLN 45 65 43 73 / 60 40 20 10
BZN 41 62 38 71 / 70 60 20 10
WEY 35 56 32 61 / 50 40 20 10
DLN 40 65 39 71 / 50 30 10 10
HVR 46 70 43 72 / 100 60 20 10
LWT 43 59 40 66 / 100 70 40 10
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
weather.gov/greatfalls
[top]
000
FXUS65 KGGW 192030
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
230 PM MDT SUN MAY 19 2013
.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH TUESDAY...
THE LOW PRESSURE CENTERS ARE CLOSING OFF AND BEGINNING TO STACK
OVER THE DAKOTAS. THE FOCUS OF PRECIPITATION IS WHERE THE
INVERTED SURFACE TROUGH NUDGES INTO THE WESTERN DAKOTAS AND
EASTERN COUNTIES OF NORTHEAST MONTANA. A BIT OF DRY SLOTTING
INITIALLY THROUGH THE CENTRAL COUNTIES OF NORTHEAST MONTANA...THEN
THE WESTERN COUNTIES AFTER MIDNIGHT WILL DIMINISH CHANCES THERE OF
ANY MEANINGFUL PRECIPITATION. EXPECT WIND TO PICK UP...MAINLY IN
THE EAST...AS THE SURFACE LOW RETROGRADES BACK TOWARDS OUR CWA.
MONDAY...THE WRAP-AROUND PRECIPITATION CONTINUES ON THE HEAVY
SIDE IN THE MORNING...BUT FINALLY AS THE LOW MOVES FARTHER EAST
THE INVERTED SURFACE TROUGH IS PULLED AWAY AND RAIN INTENSITY
DIMINISHES DURING THE AFTERNOON...BUT SHOULD CONTINUE MONDAY
NIGHT IN THE EAST. THE LOW MOVING AWAY WILL ALSO LIGHTEN THE WIND
IN THE WEST. BUT WIND IN THE EAST WILL BECOME STRONG FROM THE
NORTH DUE TO THE NEARNESS OF THE SURFACE LOW AND WIND ALOFT THAT
LINES UP. THIS WIND COULD EDGE FAR ENOUGH WEST FOR THE NEED OF A
WIND ADVISORY FOR THE EASTERN END OF FORT PECK LAKE. WILL TURN
THAT OVER TO THE OVERNIGHT SHIFT FOR ANOTHER LOOK. THERE COULD BE
SOME CLEARING IN THE NORTHWEST LATE THIS AFTERNOON AND EVENING.
TUESDAY...THE INFLUENCE OF THE LOW WILL BE TENACIOUS IN ITS REACH
INTO THE EASTERN COUNTIES OF NORTHEAST MONTANA QPF WILL LIGHT BUT
LOW OVERCAST CONTINUES. FOR THE WESTERN COUNTIES CONDITIONS WILL
BE INFLUENCED BY WEAK RIDGING BETWEEN THE DEPARTING LOW AND THE
NEXT STRONG LOW BUMPING UP AGAINST THE WASHINGTON/OREGON COAST.
TEMPERATURE DURING THE SHORT TERM WILL BE MILD AND VERY NEAR
NORMAL FOR THIS TIME OF YEAR. TEMPERATURES WILL TEND TO PUT A LID
ON THUNDERSTORM ACTIVITY...BUT WILL LEAVE ISOLATED TS IN DURING
THIS EVENINGS IN THE WEST WHERE THERE ARE A FEW GENERAL
THUNDERSTORMS. SCT
.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...
UPPER LOW OVER THE NORTHERN PLAINS EXPECTED TO SLIDE EAST BY THE
BEGINNING OF THE EXTENDED PERIOD...TO BE REPLACED BY A NARROW
UPPER RIDGE AS ANOTHER CLOSED LOW SETTLES INTO THE PACIFIC
NORTHWEST. NORTHEAST MONTANA WILL BE IN THE BOUNDARY AREA WHERE
THE SOUTHWEST FLOW AROUND THE BASE OF THE LOW MEETS THE UPPER
RIDGE. MAIN CHANCE OF RAIN WILL BE ACROSS THE WESTERN ZONES
THROUGH MIDWEEK THEN SPREAD EAST INTO THE WEEKEND AS THE MODELS
BEGIN TO OPEN UP THE LOW. EBERT
PREVIOUS LONG TERM DISCUSSION...THE EXTENDED PERIOD CONTINUES WITH
UPPER LOWS TO OUR WEST AND EAST AND CONFUSED FLOW OVER NORTHEAST
MONTANA. THIS WILL CONTINUE UNTIL FRIDAY WHEN THE UPPER LOW IN THE
PACIFIC NORTHWEST SHIFTS CLOSER TO NORTHEAST MONTANA. THIS WILL
ENHANCE THE POSSIBILITY OF THUNDERSTORMS OVER THE WEEKEND.
TEMPERATURES WILL CONTINUE AROUND NORMAL WITH HIGHS HOVERING
AROUND 70 AND LOWS IN THE UPPER 40S TO LOWER 50S THROUGH THE PERIOD.
MODEL TRENDS SHOW A FAIRLY SMOOTH RUN TO RUN PERFORMANCE WHICH
ASSISTS WITH A HIGH CONFIDENCE. DID NOT GO TOO HIGH FOR POPS OVER
THE UPCOMING WEEKEND SINCE THERE IS A HINT OF RETROGRESSION
STARTING TO SHOW UP WITH FALLING HEIGHTS IN MOST ENSEMBLES OVER
THE NORTHEAST PACIFIC. THIS COULD LEAD TO THE UPPER LOW SINKING
FURTHER SOUTH AND WEST KEEPING NORTHEAST MONTANA DRIER. OVERALL
ENSEMBLES ARE FAIRLY GOOD SINCE WE ARE IN A CLIMATOLOGICAL NORMAL
PATTERN. RMOP ARE FAIRLY GOOD WITH THE LARGE SCALE FEATURES FOR
THE EXTENDED PERIOD. THEREFORE MODERATE TO GOOD CONFIDENCE IN THE
PERIOD FROM TUESDAY NIGHT THROUGH FRIDAY WITH SOME LOWER
CONFIDENCE IN THE WEEKEND PATTERN. PROTON
&&
.AVIATION...
VFR BECOMING MVFR OVERNIGHT AS RAIN RETURNS TO THE REGION. GUSTY
NORTH WINDS ALSO EXPECTED TO PERSIST THROUGH MONDAY MORNING.
&&
.HYDROLOGY...
THE NEXT COUPLE OF DAYS WILL BE RATHER WET AS AN UPPER-LEVEL
TROUGH AFFECTS THE REGION. SEVERAL DISTURBANCES ASSOCIATED WITH THIS
TROUGH WILL PASS THROUGH WHICH WILL KEEP CHANCES FOR RAIN THROUGH
TUESDAY. MODEL GUIDANCE DEPICTS HIGH AMOUNTS OF MOISTURE WITH THIS
SYSTEM. AT THIS POINT THE ENVIRONMENT LOOKS FAVORABLE FOR SLOW-
MOVING STORMS WITH HIGHER PRECIPITATION IN LOCALIZED AREAS.
MOST OF THE BASINS IN NORTHEAST MONTANA WILL BE ABLE TO
ACCOMMODATE THIS AMOUNT OF MOISTURE. HOWEVER THERE IS SOME
CONCERN FOR RAPIDLY RISING STREAMS...FIELD FLOODING AND LOCALIZED
FLOODING IN TOWNS AS THE EVENT PERSISTS. SOME MINOR FLOODING MAY
BECOME AN ISSUE...ESPECIALLY FOR THE AREAS FROM WOLF POINT TO
CIRCLE AND EASTWARD INTO NORTH DAKOTA WHERE THE POTENTIAL FOR RAIN
IS HIGHER.
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
WEATHER.GOV/GLASGOW
000
FXUS65 KBYZ 191544
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
944 AM MDT SUN MAY 19 2013
.UPDATE...
DEEP UPPER TROUGH REMAINS OVER THE REGION TODAY AND IS BECOMING
NEGATIVELY TILTED. THE UPPER TROUGH IS ALSO CLOSING OFF AN UPPER.
CIRCULATION AROUND THE UPPER LOW IS WRAPPING PRECIPITATION INTO
OUR AREA FROM BAKER TO LIVINGSTON THIS MORNING. HAVE INCREASED
POPS ACROSS SOUTH CENTRAL AND SOUTHEAST MONTANA THIS MORNING TO
100`S AS VERY MOIST FLOW MOVING INTO THE AREA. UPPER AIR SOUNDINGS
AT GGW AND UNR SHOW PW`S NEAR 1 INCH FOR TODAY. STRONG UPPER LEVEL
FORCING ALONG WITH ISENTROPIC LIFT/BAND OF FRONTOGENESIS AND DEEP
UPSLOPE FLOW...WILL ALL COMBINE TO BRING PERIODS OF LIGHT TO
MODERATED RAINFALL ACROSS THE FORECAST AREA THE ENTIRE DAY. THE
MAJOR CONCERN CONTINUES TO BE THE BURN SCARS FROM LAST YEAR AND
WILL KEEP CURRENT FLASH FLOOD WATCH FOR THESE AREAS GOING. NO
OTHER CHANGES TO THE FORECAST FOR THIS MORNING. RICHMOND
&&
.SHORT TERM...VALID FOR TDY AND MON...
CONFIDENCE IN A SIGNIFICANT RAINFALL EVENT ACROSS MUCH OF THE AREA
OVER THE NEXT 36 TO 48 HOURS IS GROWING. ANOTHER ONE TO TWO INCHES
OF RAIN LOOKS LIKELY...AND REALISTICALLY-SPEAKING TOTALS MAY BE IN
THE 2 TO 4 INCH RANGE FROM THE BIG HORN MOUNTAINS NORTHEAST ACROSS
THE PLAINS OF FAR SOUTH CENTRAL AND MUCH OF SOUTHEASTERN MT.
AT 09 UTC...REGIONAL RADAR AND MOISTURE CHANNEL IMAGES SUGGEST THE
MID-LEVEL TROUGH IS BEGINNING TO CLOSE OFF OVER WESTERN SD...WHICH
IS WHAT ALL OF THE 00 UTC MODEL SOLUTIONS SUGGESTED WILL HAPPEN BY
MID MORNING. THOSE 00 UTC MODELS ALSO HAD A NOTABLE WESTWARD SHIFT
IN THE PLACEMENT OF THE MID- AND UPPER-LEVEL LOW WHICH IS EXPECTED
TO WOBBLE ACROSS THE DAKOTAS TODAY AND MON...AND THAT PUTS MUCH OF
THE AREA WITHIN FAVORABLE DYNAMIC FORCING FOR RAINFALL. THE 00 UTC
ECMWF ALSO MADE A SHIFT WEST AND NORTH...BUT IT IS NOT AS WET OVER
MT AS THE REST OF THE GUIDANCE HEADING INTO MON...SO WE CAUTIOUSLY
WEIGHTED THE FORECAST AWAY FROM THAT IDEA FOR NOW SINCE IT ENDS UP
AS A BIT OF AN OUTLIER.
TODAY...SHOWERS WHICH FORMED ACROSS SOUTH CENTRAL MT OVERNIGHT ARE
EXPECTED TO CONTINUE AND FILL IN FURTHER. MEANWHILE...BOTH FORCING
AND MOISTURE ADVECTION WILL INCREASE ALOFT OVER SOUTHEASTERN MT BY
MIDDAY AS THE 700-HPA LOW DEEPENS OVER WESTERN SD. CONVECTION SEEN
IN THE DAKOTAS EARLY THIS MORNING SHOULD ROTATE WESTWARD...AND NEW
PRECIPITATION WILL LIKELY FILL IN AS WELL. THE 00 UTC GFS AND GFS-
FED RAP RUNS ARE ESPECIALLY STRONG WITH THE 700-HPA LOW...AND THEY
ARE ALSO THE FARTHEST NORTHWEST MODEL SOLUTIONS WITH THIS FEATURE.
THAT IS NOT OUT OF THE QUESTION...AND IF IT ENDS UP BEING RIGHT WE
MAY EVEN HAVE OUTRIGHT HEAVY STRATIFORM RAIN BY AFTERNOON ACROSS A
GOOD PART OF THE AREA. NEEDLESS TO SAY...CATEGORICAL POPS NEAR 100
PERCENT ARE JUSTIFIED NEARLY EVERYWHERE TODAY.
TONIGHT...MOISTURE-LADEN AND DYNAMIC FORCING WILL CONTINUE FEEDING
PRECIPITATION OVER THE AREA...ESPECIALLY OVER SOUTHEASTERN MT NEAR
THE MID-LEVEL LOW...AND WHERE THE 500-300 HPA Q-VECTOR CONVERGENCE
IS STRONGEST. POPS NEAR 100 PERCENT THUS CONTINUE FOR MOST PLACES.
THE 03 UTC SREF HAS A 70 TO 90 PERCENT PROBABILITY FOR AT LEAST AN
INCH OF RAIN IN SOUTHEASTERN MT OVERNIGHT...WHICH IS NOTEWORTHY OF
AN ENSEMBLE SOLUTION. PRECIPITABLE WATER VALUES ARE EXPECTED TO BE
FROM 0.80 INCHES IN SOUTH CENTRAL MT TO AN INCH OR MORE ACROSS THE
SOUTHEASTERN PART OF MT...AND GIVEN 12 HOURS OF FORCING...RAINFALL
WILL PROBABLY BE AT LEAST NEAR THOSE VALUES IN MOST AREAS. OUR QPF
WAS INCREASED SIGNIFICANTLY OVER PREVIOUS FORECASTS...BUT IT STILL
LAGS THE 00 UTC MULTI-MODEL CONSENSUS IN SOME CASES...AND SO THERE
IS A CHANCE WE ARE STILL UNDERPLAYING TOTAL RAINFALL. THAT WILL BE
PARTICULARLY TRUE IF THE 00 UTC ECMWF ENDS UP BEING AN INCORRECTLY
DRY OUTLIER.
MON...MOISTURE SHOULD CONTINUE WRAPPING AROUND THE MID- AND UPPER-
LEVEL CIRCULATION AND BACK INTO SOUTHEASTERN MT THROUGH THE DAY. A
DRYING TREND COULD BEGIN IN SOUTH CENTRAL MT BY AFTERNOON...MAINLY
AWAY FROM UPSLOPE AREAS...AS FORECAST SOUNDINGS IN LOCALES SUCH AS
BILLINGS START SHOWING LESS SATURATION AFTER 18 UTC. IT COULD TAKE
UNTIL VERY LATE MON NIGHT OR EVEN INTO TUE THOUGH BEFORE DRYING IS
ABLE TO TAKE HOLD IN SOUTHEASTERN MT. LARGE LOWS LIKE THIS ONE ARE
OFTEN SLOWER TO MOVE THAN EXPECTED INITIALLY. THE RIDGE THAT FORMS
AT 500 HPA TO THE NORTH OF THE LOW IN SOUTHERN CANADA WILL PLAY A
BIG ROLE IN ITS SPEED SINCE IT WILL BE A BLOCKING MECHANISM.
SO...IN SUMMARY...THIS LOOKS INCREASINGLY LIKE A BIG RAIN EVENT IN
MUCH OF THE AREA. WHILE CONVECTIVE ELEMENTS WILL BE LESS LIKELY AS
WE GO FORWARD...THERE IS STILL ENSEMBLE SUPPORT FOR THREE AND SIX-
HOUR RAIN TOTALS OF A HALF INCH OR MORE IN MANY AREAS. WE CHOSE TO
ISSUE A FLASH FLOOD WATCH FOR THE BURN SCAR AREAS OF SOUTH CENTRAL
AND SOUTHEASTERN MT THROUGH 12 UTC TUE SINCE AMOUNTS LIKE THAT MAY
BE ENOUGH TO CAUSE ISSUES IN SOME OF THOSE AREAS. SCHULTZ
.LONG TERM...VALID FOR TUE...WED...THU...FRI...SAT...
CONTINUE TO SLOW THE TRANSITION TO DRIER WEATHER. MODELS
STRUGGLING WITH THE EXIT SPEED OF THE DEEP UPPER LOW CURRENTLY
PROVIDING GENEROUS PRECIPITATION TO THE FORECAST AREA. MODELS WERE
FAIRLY CONSISTENT NOW IN VERY SLOWLY SLIDING THE UPPER LOW
EASTWARD. DIFFERENCES CENTER ON THE POSITION OF THE BLOCKING HIGH
IN SOUTHERN CANADA. THE GFS WAS FARTHER SOUTH AND THUS CLEARS THE
FORECAST AREA WITH DYNAMICS SOONER THAN THE ECMWF ON TUESDAY. THE
ECMWF HAS THE BLOCKING HIGH FARTHER NORTH AND THUS LINGERS ENERGY
INTO TUESDAY OVER THE SOUTHEAST. WILL KEEP SCATTERED POPS IN THE
EAST ON TUESDAY WHILE THE WEST SHOULD EFFECTIVELY DRY OUT. LOWERED
HIGH TEMPERATURES AS THE UPPER RIDGE WAS NOT NEARLY AS AMPLIFIED
ON 00Z RUNS.
THE NEXT UPSTREAM...AND VERY DEEP...UPPER LOW OVER THE NORTHWEST
SLIDES INTO PLACE AND TURNS THE FLOW SOUTHERLY OVER SOUTHERN
MONTANA AND NORTHERN WYOMING BY WEDNESDAY. THIS WILL ESTABLISH LOW
LEVEL EASTERLY FLOW WITH LOWER SURFACE PRESSURES OVER THE GREAT
BASIN ALLOWING DEWPOINTS TO STAY UP. MODELS CONTINUE TO BACK OFF
WITH THE DRIER AIR ALOFT AND LINGER 700MB MOISTURE INTO FRIDAY NOW
AS THE UPPER LOW INCHES EASTWARD. WILL KEEP POPS MENTIONED FROM
WEDNESDAY ONWARD WITH THE BEST CHANCE OVER THE WEST CLOSER TOO THE
UPPER LOW AND UNDER THE INFLUENCE OF SLIGHTLY COOLER AIR ALOFT.
THE ECMWF WAS A LITTLE FASTER IN KICKING THE UPPER LOW NORTHEAST
ON FRIDAY BUT BOTH MODELS HAVE THE STRONGEST DYNAMICS HEADED NORTH
OF THE FORECAST AREA...SO DID NOT GO THAT HIGH WITH POPS FRIDAY
AND SATURDAY. OVERALL...COOLED THINGS DOWN A LITTLE BIT THROUGHOUT
THE EXTENDED WITH A LESS AMPLIFIED RIDGE NOW ADVERTISED BETWEEN
THE TWO DEEP UPPER LOWS. TWH
&&
.AVIATION...
ACTIVE WEATHER WILL CONTINUE TODAY AS AN AREA OF LOW PRESSURE
ALOFT MOVES SLOWLY THROUGH THE REGION. EXPECT SHOWERS AND ISOLATED
THUNDERSTORMS TODAY...WITH AREAS OF MVFR TO IFR CONDITIONS. SOME
FOG IS ALSO POSSIBLE EARLY THIS MORNING DUE TO THE ABUNDANT
SURFACE MOISTURE IN PLACE. FOG MAY REDUCE FLIGHT CONDITIONS TO IFR
OR LOWER IF IT DEVELOPS...AND THIS IS MOST LIKELY TO OCCUR IS IN
EASTERN PARTS NEAR KMLS AND KBHK. MOUNTAINS WILL BE OBSCURED. TWH
&&
.PRELIMINARY POINT TEMP/POPS...
TDY MON TUE WED THU FRI SAT
-------------------------------------------------------
BIL 058 049/061 045/069 046/069 049/072 049/074 050/075
+/T +8/R 41/B 12/T 42/T 22/T 22/T
LVM 056 046/058 038/065 040/067 040/067 041/069 042/069
9/T 86/R 41/B 14/T 44/T 43/T 33/T
HDN 059 050/061 045/070 044/071 049/074 048/077 050/077
+/T ++/R 51/E 12/T 32/T 22/T 22/T
MLS 059 051/060 046/064 046/068 050/071 050/074 052/076
+/T ++/R 53/W 12/T 22/T 22/T 22/T
4BQ 059 049/057 044/062 044/068 048/072 049/074 051/076
+/T ++/R 64/W 22/T 22/T 22/T 22/T
BHK 059 049/057 043/058 044/064 047/067 048/070 051/074
+/T ++/R 84/W 22/T 22/T 22/T 22/T
SHR 055 047/056 042/062 040/069 046/072 046/075 048/075
+/T ++/R 52/W 12/T 32/T 22/T 22/T
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...FLASH FLOOD WATCH IN EFFECT THROUGH LATE MONDAY NIGHT FOR
ZONES 29>31-36>38-57-58.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
000
FXUS65 KTFX 191540
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
940 AM MDT Sun May 19 2013
.UPDATE...
A moist northerly flow aloft continues to generate areas of light
rain over the north and eastern portions of our CWA. Precipitation
appears to be enhanced with upslope flow onto the north sides of
mountain ranges in NCentral MT. The QPF forecast from the 19/09Z
run of the SREF is consistent with present observations...so have
raised POPs and QPF a bit further west as progged over central MT and
along the hiline. Temperatures and other elements are in line with
going forecast.
&&
.DISCUSSION...
&&
.AVIATION...
UPDATED 1135Z.
Slight instability and widespread moisture will keep skies BKN-OVC
across southwest and central MT with mix of VFR/MVFR ceilings today.
Scattered showers expected near all TAF sites through the day with
occasional periods of light rain. Ceilings may briefly drop to IFR
category while precipitation is occurring. There is also a slight
chance for a few short-lived thunderstorms to develop this aftn, but
probabilities currently too low to mention in latest TAFs. Light
winds expected today.
Waranauskas
&&
.HYDROLOGY...
First of two slow moving upper level low pressure systems will
bring widespread showers to much of north central and SW MT
through Monday with the second upper level low moving to a position
over the Pacific NW Wednesday and remaining nearly stationary into
next weekend bringing additional precipitation to the region. Cooler
temperatures have reduced snowmelt from higher elevations, however
there are still concerns that rain on the melting snowpack may cause
enhanced rises in stream/river levels in some areas. Most area
rivers are currently well below flood stage but some smaller
tributaries are likely near or approaching bankfull, so rainfall
totals and river stage forecasts will be closely monitored for
significant changes and impacts. Hoenisch
&&
.PREV DISCUSSION...
/ISSUED 535 AM MDT Sun May 19 2013/
Today through Tuesday...A slow moving upper level trough,
extending from the Pacific NW southeast into the Southern Rockies
will continue its slow progression east today, with the upper
trough consolidating into a broad closed circulation over the
Northern Plains/Upper Midwest states tonight through Monday. This
will keep a moist northerly flow aloft over the region through
Monday as the forecast area remains on the NW side of the upper
level low. Model differences have improved somewhat from previous
days with the location of weak energy within the broad upper level
circulation that will focus areas of more persistent precipitation
within the overall cloudy/showery pattern. However confidence has
only increased to moderate levels for the location of local
precipitation maximums over the next 36 hrs. In general, eastern
portions of Central/North-central MT will see the most persistent
shower activity through Monday where additional precipitation
amounts of over a half inch are expected from the Bears Paw Mtns
SW through the Little Belts and Snowies, including the Judith
Basin and Lewistown areas. Elsewhere over North-Central MT and
east of I-15 in central/SW MT about 0.25" to 0.50" of
precipitation is expected with lesser amounts for areas west of
I-15. Temperatures will continue slightly below seasonal averages
with drier and warmer conditions moving into the forecast area
Monday night through Tuesday as weak upper level ridging moves
over the Northern Rockies. Hoenisch
Tuesday Night through Sunday...Only slight changes noted in forecast
model solutions from previous runs for this period. Two elements, a
ridge of high pressure centered in Saskatchewan extending into the
Upper Midwest states and a closed upper level low pressure system
over the PacNW will be the main weather features for our region.
Neither feature moves much until late next weekend, leaving us in a
persistent pattern of mild and moist southerly flow that will
produce partly to mostly cloudy skies with a chance of light rain
almost every day. Timing for the precipitation remains a bit elusive
at this point, as models continue to show the PacNW system making a
big, slow loop from the Pacific coast thru WA/OR then back into
BC/Alb. Shortwave trofs spinning off the main low center generally
stay along/west of the Continental Divide, but pronounced east-
southeast flow at the low- and mid-levels east of the Divide is
expected to pull moisture around the base of the Canadian high and
across MT, leading to upslope (cloudy) conditions and the
aforementioned periods of light rain. The one notable difference
from the earlier model runs is that both the GFS and ECMWF now push
a cool front thru our region on Friday. The front will be
accompanied by a negatively-tilted (oriented NW-SE) trof and a
possibly some jet stream effects, which typically leads to better
chances of thunderstorms and higher rainfall amounts, which the
models are indeed suggesting at this point. Will keep an eye on how
the models handle the evolution of the Friday conditions,
particularly for the precipitation totals and what effect that will
have on our local streams/rivers. The overall pattern begins to
modify on Sunday with the Canadian high pushing east and the PacNW
low weakening and also tracking east along the US/Can border,
setting up a more typical westerly flow regime. Lastly, expect high
temperatures to remain close to normal (mid 60s) each day this week.
Waranauskas
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 62 44 64 42 / 70 70 60 20
CTB 61 43 64 42 / 80 70 50 20
HLN 62 45 65 43 / 70 60 40 20
BZN 57 41 62 38 / 80 70 60 20
WEY 49 35 56 32 / 80 50 40 20
DLN 56 40 65 39 / 60 50 30 10
HVR 64 46 70 43 / 100 100 60 20
LWT 56 43 59 40 / 100 100 70 40
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
weather.gov/greatfalls
000
FXUS65 KGGW 191520 AAA
AFDGGW
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GLASGOW MT
920 AM MDT SUN MAY 19 2013
.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH TUESDAY...
THE LOW PRESSURE CENTERS ARE CLOSING OFF AND BEGINNING TO STACK
OVER THE WESTERN DAKOTAS WHERE THE FOCUS OF PRECIPITATION IS THIS
MORNING. A BIT OF DRY SLOTTING THROUGH THE CENTRAL COUNTIES OF
NORTHEAST MONTANA PROMPTED SOME ADJUSTMENTS TO POPS/QPF AND WX FOR
TODAY. EXPECT WIND TO PICK UP AS THE SURFACE LOW RETROGRADES BACK
TOWARDS OUR CWA. AS IT DOES THE INVERTED SURFACE TROUGH NUDGES
INTO NEMONT BRINGING HEAVIER RAIN AND SOME THUNDERSTORMS BY LATE
AFTERNOON. ADJUSTED WIND BASED ON OBSERVATIONS AND THE LATEST
GUIDANCE. TEMPERATURES LOOK GOOD SO NO ADJUSTMENTS THERE. SCT
PREVIOUS DISCUSSION...
TODAY THROUGH MONDAY NIGHT...UPPER LEVEL TROUGH WILL CONTINUE TO
PROVIDE UNSETTLED WEATHER CONDITIONS FOR NE MT. A SURFACE LOW
PRESSURE SYSTEM WILL CONTINUE TO SIT AND SPIN AS IT BECOMES
VERTICALLY STACKED OVER EASTERN SOUTH DAKOTA BY MONDAY. THIS LOW
PRESSURE WILL CONTINUE TO PUMP EASTERLY SURFACE FLOW INTO THE CWA
WHICH WITH COMBINED WITH LOBES OF UPPER LEVEL SHORTWAVE ENERGY
SWIRLING AROUND THE TROUGH...WILL HELP PROVIDE THE SUPPORT FOR A
CONTINUATION OF VERY STEADY RAIN SHOWERS. LOOKING AT NAM BUFR
FORECAST SOUNDINGS...DO NOTE THAT LI IS NEAR 0 IN SOME LOCATIONS
DURING SUNDAY AFTERNOON WITH TOTAL TOTALS HOVERING AROUND 50.
GIVEN THE CONVECTIVE NATURE OF THE PULSES OF SHOWER ACTIVITY THAT
HAVE OCCURRED THE PAST COUPLE OF DAYS HOWEVER...AM NOT COMPLETELY
SOLD ON THE IDEA THAT THUNDER WILL NOT AT ALL BE A POSSIBILITY.
WITH THE STEADY RAINS...DO FEEL EMBEDDED THUNDER IS A POSSIBILITY
AND SO KEPT IN A SLIGHT MENTION OF IT. SOUNDINGS ARE ALSO SHOWING
AN INCH OR MORE PRECIPITABLE WATER THROUGH THIS PERIOD AND SO
THERE IS CERTAINLY PLENTY OF MOISTURE IN THE VERTICAL TO WORK
WITH.
MODEL GUIDANCE HAS BEEN FAIRLY CONSISTENT WITH THE STEADY
RAINS AFFECTING MUCH OF THE CWA THROUGH MONDAY NIGHT...BUT
PREFERRED THE ECMWF AND THE HRRR SOLUTIONS GIVEN EXCELLENT RUN TO
RUN CONTINUITY. WILL EXPECT THE HEAVIEST RAINFALL AMOUNTS IN THE
SOUTHEASTERN ZONES CLOSER TO THE SURFACE LOW...BUT ISOLATED HIGHER
RAINFALL TOTALS MAY OCCUR WHERE THUNDER AND/OR THE STEADIEST
RAINFALL DOES OCCUR. THAT WILL LARGELY DEPEND UPON MESOSCALE
DETAILS THAT ARE COMPLEX AND DIFFICULT TO PINPOINT AT THIS TIME.
CERTAINLY THERE WILL LIKELY BE A WIDESPREAD WETTING RAIN ACROSS
THE CWA THROUGH MONDAY NIGHT...BUT ISOLATED LOCATIONS MAY PICK UP
AN ADDITIONAL ONE TO TWO INCHES OF RAINFALL.
TUESDAY...THE RAIN SLOWLY EXITS THE FORECAST REGION FROM WEST TO
EAST. HAVE DROPPED OFF POPS ACCORDINGLY DURING THE DAY ON TUESDAY
AND ESPECIALLY TUESDAY NIGHT. WITH LITTLE CHANGE IN THE FORECAST
850MB TEMPERATURES...WILL NOT EXPECT MUCH IN THE WAY OF SWINGS.
EXPECTING SEASONAL CONDITIONS THROUGH THE ENTIRE SHORT TERM
PERIOD...OR PERHAPS SLIGHTLY BELOW AVERAGE WITH THE LARGE TROUGH
IN PLACE. MALIAWCO
.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...
THE EXTENDED PERIOD CONTINUES WITH UPPER LOWS TO OUR WEST AND EAST
AND CONFUSED FLOW OVER NORTHEAST MONTANA. THIS WILL CONTINUE UNTIL
FRIDAY WHEN THE UPPER LOW IN THE PACIFIC NORTHWEST SHIFTS CLOSER
TO NORTHEAST MONTANA. THIS WILL ENHANCE THE POSSIBILITY OF
THUNDERSTORMS OVER THE WEEKEND.
TEMPERATURES WILL CONTINUE AROUND NORMAL WITH HIGHS HOVERING
AROUND 70 AND LOWS IN THE UPPER 40S TO LOWER 50S THROUGH THE PERIOD.
MODEL TRENDS SHOW A FAIRLY SMOOTH RUN TO RUN PERFORMANCE WHICH
ASSISTS WITH A HIGH CONFIDENCE. DID NOT GO TOO HIGH FOR POPS OVER
THE UPCOMING WEEKEND SINCE THERE IS A HINT OF RETROGRESSION
STARTING TO SHOW UP WITH FALLING HEIGHTS IN MOST ENSEMBLES OVER
THE NORTHEAST PACIFIC. THIS COULD LEAD TO THE UPPER LOW SINKING
FURTHER SOUTH AND WEST KEEPING NORTHEAST MONTANA DRIER. OVERALL
ENSEMBLES ARE FAIRLY GOOD SINCE WE ARE IN A CLIMATOLOGICAL NORMAL
PATTERN. RMOP ARE FAIRLY GOOD WITH THE LARGE SCALE FEATURES FOR
THE EXTENDED PERIOD. THEREFORE MODERATE TO GOOD CONFIDENCE IN THE
PERIOD FROM TUESDAY NIGHT THROUGH FRIDAY WITH SOME LOWER
CONFIDENCE IN THE WEEKEND PATTERN. PROTON
&&
.AVIATION...
MVFR. MODELS HAVE BEEN A LITTLE LOW ON CEILING HEIGHTS AT ALL
LOCATIONS FOR PAST 48 HOURS AND LOOK TO CONTINUE THE TREND FOR THE
NEXT 24 HOURS. WILL MAINTAIN MVFR AT MOST LOCATIONS WITH LOW VFR
FOR GLASGOW THROUGH THE PERIOD. COOLER TEMPERATURES ALOFT WILL
CONTINUE THE SHOWERY CONDITIONS THROUGH THE PERIOD. PROTON
&&
.HYDROLOGY...
THE NEXT FEW DAYS WILL BE RATHER WET AS AN UPPER-LEVEL TROUGH
AFFECTS THE AREA. SEVERAL DISTURBANCES ASSOCIATED WITH THIS
TROUGH WILL PASS THROUGH WHICH WILL KEEP CHANCES FOR RAIN WITH
SOME THUNDERSTORMS THROUGH EARLY NEXT WEEK. MODEL GUIDANCE DEPICTS
HIGH AMOUNTS OF MOISTURE WITH THIS SYSTEM. AT THIS POINT THE
ENVIRONMENT LOOKS FAVORABLE FOR SLOW-MOVING STORMS WITH HIGHER
PRECIPITATION IN LOCALIZED AREAS.
MOST OF THE BASINS IN NORTHEAST MONTANA WILL BE ABLE TO
ACCOMMODATE THIS AMOUNT OF MOISTURE...AT LEAST EARLY ON IN THE
EVENT. THERE IS SOME CONCERN FOR RAPIDLY RISING STREAMS...FIELD
FLOODING AND LOCALIZED FLOODING IN TOWNS AS THE EVENT PERSISTS.
SOME MINOR FLOODING MAY BECOME AN ISSUE... ESPECIALLY FOR THE
AREAS FROM GLASGOW TO CIRCLE AND EASTWARD INTO NORTH DAKOTA WHERE
THE POTENTIAL FOR STRONGER THUNDERSTORMS IS HIGHER.
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
WEATHER.GOV/GLASGOW
000
FXUS65 KTFX 191141
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
535 AM MDT Sun May 19 2013
AVIATION SECTION UPDATED
.DISCUSSION...
Today through Tuesday...A slow moving upper level trough,
extending from the Pacific NW southeast into the Southern Rockies
will continue its slow progression east today, with the upper
trough consolidating into a broad closed circulation over the
Northern Plains/Upper Midwest states tonight through Monday. This
will keep a moist northerly flow aloft over the region through
Monday as the forecast area remains on the NW side of the upper
level low. Model differences have improved somewhat from previous
days with the location of weak energy within the broad upper level
circulation that will focus areas of more persistent precipitation
within the overall cloudy/showery pattern. However confidence has
only increased to moderate levels for the location of local
precipitation maximums over the next 36 hrs. In general, eastern
portions of Central/North-central MT will see the most persistent
shower activity through Monday where additional precipitation
amounts of over a half inch are expected from the Bears Paw Mtns
SW through the Little Belts and Snowies, including the Judith
Basin and Lewistown areas. Elsewhere over North-Central MT and
east of I-15 in central/SW MT about 0.25" to 0.50" of
precipitation is expected with lesser amounts for areas west of
I-15. Temperatures will continue slightly below seasonal averages
with drier and warmer conditions moving into the forecast area
Monday night through Tuesday as weak upper level ridging moves
over the Northern Rockies. Hoenisch
Tuesday Night through Sunday...Only slight changes noted in forecast
model solutions from previous runs for this period. Two elements, a
ridge of high pressure centered in Saskatchewan extending into the
Upper Midwest states and a closed upper level low pressure system
over the PacNW will be the main weather features for our region.
Neither feature moves much until late next weekend, leaving us in a
persistent pattern of mild and moist southerly flow that will
produce partly to mostly cloudy skies with a chance of light rain
almost every day. Timing for the precipitation remains a bit elusive
at this point, as models continue to show the PacNW system making a
big, slow loop from the Pacific coast thru WA/OR then back into
BC/Alb. Shortwave trofs spinning off the main low center generally
stay along/west of the Continental Divide, but pronounced east-
southeast flow at the low- and mid-levels east of the Divide is
expected to pull moisture around the base of the Canadian high and
across MT, leading to upslope (cloudy) conditions and the
aforementioned periods of light rain. The one notable difference
from the earlier model runs is that both the GFS and ECMWF now push
a cool front thru our region on Friday. The front will be
accompanied by a negatively-tilted (oriented NW-SE) trof and a
possibly some jet stream effects, which typically leads to better
chances of thunderstorms and higher rainfall amounts, which the
models are indeed suggesting at this point. Will keep an eye on how
the models handle the evolution of the Friday conditions,
particularly for the precipitation totals and what effect that will
have on our local streams/rivers. The overall pattern begins to
modify on Sunday with the Canadian high pushing east and the PacNW
low weakening and also tracking east along the US/Can border,
setting up a more typical westerly flow regime. Lastly, expect high
temperatures to remain close to normal (mid 60s) each day this week.
Waranauskas
&&
.AVIATION...
UPDATED 1135Z.
Slight instability and widespread moisture will keep skies BKN-OVC
across southwest and central MT with mix of VFR/MVFR ceilings today.
Scattered showers expected near all TAF sites through the day with
occasional periods of light rain. Ceilings may briefly drop to IFR
category while precipitation is occurring. There is also a slight
chance for a few short-lived thunderstorms to develop this aftn, but
probabilities currently too low to mention in latest TAFs. Light
winds expected today.
Waranauskas
&&
.HYDROLOGY...
First of two slow moving upper level low pressure systems will
bring widespread showers to much of north central and SW MT
through Monday with the second upper level low moving to a position
over the Pacific NW Wednesday and remaining nearly stationary into
next weekend bringing additional precipitation to the region. Cooler
temperatures have reduced snowmelt from higher elevations, however
there are still concerns that rain on the melting snowpack may cause
enhanced rises in stream/river levels in some areas. Most area
rivers are currently well below flood stage but some smaller
tributaries are likely near or approaching bankfull, so rainfall
totals and river stage forecasts will be closely monitored for
significant changes and impacts. Hoenisch
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 62 44 64 42 / 60 70 60 20
CTB 61 43 64 42 / 70 70 50 20
HLN 62 45 65 43 / 50 60 40 20
BZN 57 41 62 38 / 70 60 60 20
WEY 49 35 56 32 / 70 50 40 20
DLN 56 40 65 39 / 50 50 30 10
HVR 64 46 70 43 / 100 80 60 20
LWT 56 43 59 40 / 100 90 70 40
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...HOENISCH
LONG TERM...WARANAUSKAS
AVIATION...WARANAUSKAS
weather.gov/greatfalls
000
FXUS65 KTFX 191020
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
420 AM MDT Sun May 19 2013
.DISCUSSION...
Today through Tuesday...A slow moving upper level trough,
extending from the Pacific NW southeast into the Southern Rockies
will continue its slow progression east today, with the upper
trough consolidating into a broad closed circulation over the
Northern Plains/Upper Midwest states tonight through Monday. This
will keep a moist northerly flow aloft over the region through
Monday as the forecast area remains on the NW side of the upper
level low. Model differences have improved somewhat from previous
days with the location of weak energy within the broad upper level
circulation that will focus areas of more persistent precipitation
within the overall cloudy/showery pattern. However confidence has
only increased to moderate levels for the location of local
precipitation maximums over the next 36 hrs. In general, eastern
portions of Central/North-central MT will see the most persistent
shower activity through Monday where additional precipitation
amounts of over a half inch are expected from the Bears Paw Mtns
SW through the Little Belts and Snowies, including the Judith
Basin and Lewistown areas. Elsewhere over North-Central MT and
east of I-15 in central/SW MT about 0.25" to 0.50" of
precipitation is expected with lesser amounts for areas west of
I-15. Temperatures will continue slightly below seasonal averages
with drier and warmer conditions moving into the forecast area
Monday night through Tuesday as weak upper level ridging moves
over the Northern Rockies. Hoenisch
Tuesday Night through Sunday...Only slight changes noted in forecast
model solutions from previous runs for this period. Two elements, a
ridge of high pressure centered in Saskatchewan extending into the
Upper Midwest states and a closed upper level low pressure system
over the PacNW will be the main weather features for our region.
Neither feature moves much until late next weekend, leaving us in a
persistent pattern of mild and moist southerly flow that will
produce partly to mostly cloudy skies with a chance of light rain
almost every day. Timing for the precipitation remains a bit elusive
at this point, as models continue to show the PacNW system making a
big, slow loop from the Pacific coast thru WA/OR then back into
BC/Alb. Shortwave trofs spinning off the main low center generally
stay along/west of the Continental Divide, but pronounced east-
southeast flow at the low- and mid-levels east of the Divide is
expected to pull moisture around the base of the Canadian high and
across MT, leading to upslope (cloudy) conditions and the
aforementioned periods of light rain. The one notable difference
from the earlier model runs is that both the GFS and ECMWF now push
a cool front thru our region on Friday. The front will be
accompanied by a negatively-tilted (oriented NW-SE) trof and a
possibly some jet stream effects, which typically leads to better
chances of thunderstorms and higher rainfall amounts, which the
models are indeed suggesting at this point. Will keep an eye on how
the models handle the evolution of the Friday conditions,
particularly for the precipitation totals and what effect that will
have on our local streams/rivers. The overall pattern begins to
modify on Sunday with the Canadian high pushing east and the PacNW
low weakening and also tracking east along the US/Can border,
setting up a more typical westerly flow regime. Lastly, expect high
temperatures to remain close to normal (mid 60s) each day this week.
Waranauskas
&&
.AVIATION...
UPDATED 0500Z.
Unsettled weather continues for the next 24 hours as rain showers
are expected to remain in the area for the entire TAF period. An
isolated thunderstorm is still possible...however not expecting any
long duration impacts so no VCTS or TSRA in the TAFs. Ceilings and
visibilities should remain VFR but brief MVFR/IFR conditions are
possible near any precipitation areas. Suk
&&
.HYDROLOGY...
First of two slow moving upper level low pressure systems will
bring widespread showers to much of north central and SW MT
through Monday with the second upper level low moving to a
position over the Pacific NW Wednesday and remaining nearly stationary
into next weekend bringing additional precipitation to the region.
Cooler temperatures have reduced snowmelt from higher elevations,
however there are still concerns that rain on the melting snowpack
may cause enhanced rises in stream/river levels in some areas.
Most area rivers are currently well below flood stage but some
smaller tributaries are likely near or approaching bankfull, so
rainfall totals and river stage forecasts will be closely
monitored for significant changes and impacts. Hoenisch
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 62 44 64 42 / 60 70 60 20
CTB 61 43 64 42 / 70 70 50 20
HLN 62 45 65 43 / 50 60 40 20
BZN 57 41 62 38 / 70 60 60 20
WEY 49 35 56 32 / 70 50 40 20
DLN 56 40 65 39 / 50 50 30 10
HVR 64 46 70 43 / 100 80 60 20
LWT 56 43 59 40 / 100 90 70 40
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...HOENISCH
LONG TERM...WARANAUSKAS
AVIATION...WARANAUSKAS
weather.gov/greatfalls
000
FXUS65 KMSO 190955
AFDMSO
Area Forecast Discussion
National Weather Service Missoula MT
355 AM MDT Sun May 19 2013
.DISCUSSION...Rain will once again be the predominant feature
again today, with the most prominent coverage remaining along the
Continental Divide this morning. Showers will then gradually shift
westward, encompassing most of western Montana and central Idaho
by this afternoon. The good news is: this should be the last round
of rainfall we see today, with a break expected Monday and Tuesday
under brief high pressure. Temperatures will remain cool today,
but as drier conditions return on Monday and Tuesday, high temps
will rebound into the 70s through Tuesday. Enjoy the warmth and
reappearance of the sun, because rain, and many days of it, will
once again return on Wednesday.
Wednesday through Friday...Forecast models continue to advertise
the development of a deep low pressure system over the Pacific
Northwest. This low remains nearly stationary through the second
half of next week and will present concerns to the Northern Rockies
region.
First, considerable moisture will be circulating around the low
center. At the present time, the main targets are Glacier
National Park and the Bob Marshall Wilderness areas, with moderate
to heavy rainfall. Contributions from significant rainfall and
accelerated snow melt due to warm temperatures poses a real threat
for increased runoff and rising rivers and small streams levels
across northwest Montana by the end of the week.
Secondly, the atmosphere ahead of the low pressure system will be
warm, moist, and unstable. Thunderstorms will be part of the
forecast, but whether or not storms become severe is still in
question.
Finally, snow over Lookout and Lolo mountain passes is a
possibility and could be an impact to travel and recreational
enthusiasts who are tempted to head into the mountains across the
Idaho Panhandle and adjacent Montana mountains.
&&
.AVIATION...The atmosphere remains moist and quite unstable and
showers will redevelop during the day as temperatures warm at the
surface. There will be some precipitation moving across the
Continental Divide and into west-central Montana this morning. Mountains
will obscured at times in clouds and precipitation, especially
during the afternoon and evening hours. All airfields will be
impacted by showers and lower ceilings from time to time. Shower
activity will decrease once the sun dips below the horizon.
Overall conditions will be improving tonight.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&
$$
Follow us on Facebook and Twitter!
https://www.facebook.com/US.NationalWeatherService.Missoula.gov
https://www.twitter.com/NWSMissoula
000
FXUS65 KGGW 190952
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
352 AM MDT SUN MAY 19 2013
.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH TUESDAY...
TODAY THROUGH MONDAY NIGHT...UPPER LEVEL TROUGH WILL CONTINUE TO
PROVIDE UNSETTLED WEATHER CONDITIONS FOR NE MT. A SURFACE LOW
PRESSURE SYSTEM WILL CONTINUE TO SIT AND SPIN AS IT BECOMES
VERTICALLY STACKED OVER EASTERN SOUTH DAKOTA BY MONDAY. THIS LOW
PRESSURE WILL CONTINUE TO PUMP EASTERLY SURFACE FLOW INTO THE CWA
WHICH WITH COMBINED WITH LOBES OF UPPER LEVEL SHORTWAVE ENERGY
SWIRLING AROUND THE TROUGH...WILL HELP PROVIDE THE SUPPORT FOR A
CONTINUATION OF VERY STEADY RAIN SHOWERS. LOOKING AT NAM BUFR
FORECAST SOUNDINGS...DO NOTE THAT LI IS NEAR 0 IN SOME LOCATIONS
DURING SUNDAY AFTERNOON WITH TOTAL TOTALS HOVERING AROUND 50.
GIVEN THE CONVECTIVE NATURE OF THE PULSES OF SHOWER ACTIVITY THAT
HAVE OCCURRED THE PAST COUPLE OF DAYS HOWEVER...AM NOT COMPLETELY
SOLD ON THE IDEA THAT THUNDER WILL NOT AT ALL BE A POSSIBILITY.
WITH THE STEADY RAINS...DO FEEL EMBEDDED THUNDER IS A POSSIBILITY
AND SO KEPT IN A SLIGHT MENTION OF IT. SOUNDINGS ARE ALSO SHOWING
AN INCH OR MORE PRECIPITABLE WATER THROUGH THIS PERIOD AND SO
THERE IS CERTAINLY PLENTY OF MOISTURE IN THE VERTICAL TO WORK
WITH.
MODEL GUIDANCE HAS BEEN FAIRLY CONSISTENT WITH THE STEADY
RAINS AFFECTING MUCH OF THE CWA THROUGH MONDAY NIGHT...BUT
PREFERRED THE ECMWF AND THE HRRR SOLUTIONS GIVEN EXCELLENT RUN TO
RUN CONTINUITY. WILL EXPECT THE HEAVIEST RAINFALL AMOUNTS IN THE
SOUTHEASTERN ZONES CLOSER TO THE SURFACE LOW...BUT ISOLATED HIGHER
RAINFALL TOTALS MAY OCCUR WHERE THUNDER AND/OR THE STEADIEST
RAINFALL DOES OCCUR. THAT WILL LARGELY DEPEND UPON MESOSCALE
DETAILS THAT ARE COMPLEX AND DIFFICULT TO PINPOINT AT THIS TIME.
CERTAINLY THERE WILL LIKELY BE A WIDESPREAD WETTING RAIN ACROSS
THE CWA THROUGH MONDAY NIGHT...BUT ISOLATED LOCATIONS MAY PICK UP
AN ADDITIONAL ONE TO TWO INCHES OF RAINFALL.
TUESDAY...THE RAIN SLOWLY EXITS THE FORECAST REGION FROM WEST TO
EAST. HAVE DROPPED OFF POPS ACCORDINGLY DURING THE DAY ON TUESDAY
AND ESPECIALLY TUESDAY NIGHT. WITH LITTLE CHANGE IN THE FORECAST
850MB TEMPERATURES...WILL NOT EXPECT MUCH IN THE WAY OF SWINGS.
EXPECTING SEASONAL CONDITIONS THROUGH THE ENTIRE SHORT TERM
PERIOD...OR PERHAPS SLIGHTLY BELOW AVERAGE WITH THE LARGE TROUGH
IN PLACE. MALIAWCO
.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...
THE EXTENDED PERIOD CONTINUES WITH UPPER LOWS TO OUR WEST AND EAST
AND CONFUSED FLOW OVER NORTHEAST MONTANA. THIS WILL CONTINUE UNTIL
FRIDAY WHEN THE UPPER LOW IN THE PACIFIC NORTHWEST SHIFTS CLOSER
TO NORTHEAST MONTANA. THIS WILL ENHANCE THE POSSIBILITY OF
THUNDERSTORMS OVER THE WEEKEND.
TEMPERATURES WILL CONTINUE AROUND NORMAL WITH HIGHS HOVERING
AROUND 70 AND LOWS IN THE UPPER 40S TO LOWER 50S THROUGH THE PERIOD.
MODEL TRENDS SHOW A FAIRLY SMOOTH RUN TO RUN PERFORMANCE WHICH
ASSISTS WITH A HIGH CONFIDENCE. DID NOT GO TOO HIGH FOR POPS OVER
THE UPCOMING WEEKEND SINCE THERE IS A HINT OF RETROGRESSION
STARTING TO SHOW UP WITH FALLING HEIGHTS IN MOST ENSEMBLES OVER
THE NORTHEAST PACIFIC. THIS COULD LEAD TO THE UPPER LOW SINKING
FURTHER SOUTH AND WEST KEEPING NORTHEAST MONTANA DRIER. OVERALL
ENSEMBLES ARE FAIRLY GOOD SINCE WE ARE IN A CLIMATOLOGICAL NORMAL
PATTERN. RMOP ARE FAIRLY GOOD WITH THE LARGE SCALE FEATURES FOR
THE EXTENDED PERIOD. THEREFORE MODERATE TO GOOD CONFIDENCE IN THE
PERIOD FROM TUESDAY NIGHT THROUGH FRIDAY WITH SOME LOWER
CONFIDENCE IN THE WEEKEND PATTERN. PROTON
&&
.AVIATION...
MVFR. MODELS HAVE BEEN A LITTLE LOW ON CEILING HEIGHTS AT ALL
LOCATIONS FOR PAST 48 HOURS AND LOOK TO CONTINUE THE TREND FOR THE
NEXT 24 HOURS. WILL MAINTAIN MVFR AT MOST LOCATIONS WITH LOW VFR
FOR GLASGOW THROUGH THE PERIOD. COOLER TEMPERATURES ALOFT WILL
CONTINUE THE SHOWERY CONDITIONS THROUGH THE PERIOD. PROTON
&&
.HYDROLOGY...
THE NEXT FEW DAYS WILL BE RATHER WET AS AN UPPER-LEVEL TROUGH
AFFECTS THE AREA. SEVERAL DISTURBANCES ASSOCIATED WITH THIS TROUGH
WILL PASS THROUGH WHICH WILL KEEP CHANCES FOR RAIN WITH SOME
THUNDERSTORMS THROUGH EARLY NEXT WEEK. MODEL GUIDANCE DEPICTS HIGH
AMOUNTS OF MOISTURE WITH THIS SYSTEM. AT THIS POINT THE
ENVIRONMENT LOOKS FAVORABLE FOR SLOW-MOVING STORMS WITH HIGHER
PRECIPITATION IN LOCALIZED AREAS.
MOST OF THE BASINS IN NORTHEAST MONTANA WILL BE ABLE TO ACCOMMODATE
THIS AMOUNT OF MOISTURE... AT LEAST EARLY ON IN THE EVENT. THERE IS
SOME CONCERN FOR RAPIDLY RISING STREAMS...FIELD FLOODING AND
LOCALIZED FLOODING IN TOWNS AS THE EVENT PERSISTS. SOME MINOR
FLOODING MAY BECOME AN ISSUE... ESPECIALLY FOR THE AREAS FROM
GLASGOW TO CIRLE AND EASTWARD INTO NORTH DAKOTA WHERE THE POTENTIAL
FOR STRONGER THUNDERSTORMS IS HIGHER.
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
WEATHER.GOV/GLASGOW
000
FXUS65 KBYZ 190950
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
350 AM MDT SUN MAY 19 2013
.SHORT TERM...VALID FOR TDY AND MON...
CONFIDENCE IN A SIGNIFICANT RAINFALL EVENT ACROSS MUCH OF THE AREA
OVER THE NEXT 36 TO 48 HOURS IS GROWING. ANOTHER ONE TO TWO INCHES
OF RAIN LOOKS LIKELY...AND REALISTICALLY-SPEAKING TOTALS MAY BE IN
THE 2 TO 4 INCH RANGE FROM THE BIG HORN MOUNTAINS NORTHEAST ACROSS
THE PLAINS OF FAR SOUTH CENTRAL AND MUCH OF SOUTHEASTERN MT.
AT 09 UTC...REGIONAL RADAR AND MOISTURE CHANNEL IMAGES SUGGEST THE
MID-LEVEL TROUGH IS BEGINNING TO CLOSE OFF OVER WESTERN SD...WHICH
IS WHAT ALL OF THE 00 UTC MODEL SOLUTIONS SUGGESTED WILL HAPPEN BY
MID MORNING. THOSE 00 UTC MODELS ALSO HAD A NOTABLE WESTWARD SHIFT
IN THE PLACEMENT OF THE MID- AND UPPER-LEVEL LOW WHICH IS EXPECTED
TO WOBBLE ACROSS THE DAKOTAS TODAY AND MON...AND THAT PUTS MUCH OF
THE AREA WITHIN FAVORABLE DYNAMIC FORCING FOR RAINFALL. THE 00 UTC
ECMWF ALSO MADE A SHIFT WEST AND NORTH...BUT IT IS NOT AS WET OVER
MT AS THE REST OF THE GUIDANCE HEADING INTO MON...SO WE CAUTIOUSLY
WEIGHTED THE FORECAST AWAY FROM THAT IDEA FOR NOW SINCE IT ENDS UP
AS A BIT OF AN OUTLIER.
TODAY...SHOWERS WHICH FORMED ACROSS SOUTH CENTRAL MT OVERNIGHT ARE
EXPECTED TO CONTINUE AND FILL IN FURTHER. MEANWHILE...BOTH FORCING
AND MOISTURE ADVECTION WILL INCREASE ALOFT OVER SOUTHEASTERN MT BY
MIDDAY AS THE 700-HPA LOW DEEPENS OVER WESTERN SD. CONVECTION SEEN
IN THE DAKOTAS EARLY THIS MORNING SHOULD ROTATE WESTWARD...AND NEW
PRECIPITATION WILL LIKELY FILL IN AS WELL. THE 00 UTC GFS AND GFS-
FED RAP RUNS ARE ESPECIALLY STRONG WITH THE 700-HPA LOW...AND THEY
ARE ALSO THE FARTHEST NORTHWEST MODEL SOLUTIONS WITH THIS FEATURE.
THAT IS NOT OUT OF THE QUESTION...AND IF IT ENDS UP BEING RIGHT WE
MAY EVEN HAVE OUTRIGHT HEAVY STRATIFORM RAIN BY AFTERNOON ACROSS A
GOOD PART OF THE AREA. NEEDLESS TO SAY...CATEGORICAL POPS NEAR 100
PERCENT ARE JUSTIFIED NEARLY EVERYWHERE TODAY.
TONIGHT...MOISTURE-LADEN AND DYNAMIC FORCING WILL CONTINUE FEEDING
PRECIPITATION OVER THE AREA...ESPECIALLY OVER SOUTHEASTERN MT NEAR
THE MID-LEVEL LOW...AND WHERE THE 500-300 HPA Q-VECTOR CONVERGENCE
IS STRONGEST. POPS NEAR 100 PERCENT THUS CONTINUE FOR MOST PLACES.
THE 03 UTC SREF HAS A 70 TO 90 PERCENT PROBABILITY FOR AT LEAST AN
INCH OF RAIN IN SOUTHEASTERN MT OVERNIGHT...WHICH IS NOTEWORTHY OF
AN ENSEMBLE SOLUTION. PRECIPITABLE WATER VALUES ARE EXPECTED TO BE
FROM 0.80 INCHES IN SOUTH CENTRAL MT TO AN INCH OR MORE ACROSS THE
SOUTHEASTERN PART OF MT...AND GIVEN 12 HOURS OF FORCING...RAINFALL
WILL PROBABLY BE AT LEAST NEAR THOSE VALUES IN MOST AREAS. OUR QPF
WAS INCREASED SIGNIFICANTLY OVER PREVIOUS FORECASTS...BUT IT STILL
LAGS THE 00 UTC MULTI-MODEL CONSENSUS IN SOME CASES...AND SO THERE
IS A CHANCE WE ARE STILL UNDERPLAYING TOTAL RAINFALL. THAT WILL BE
PARTICULARLY TRUE IF THE 00 UTC ECMWF ENDS UP BEING AN INCORRECTLY
DRY OUTLIER.
MON...MOISTURE SHOULD CONTINUE WRAPPING AROUND THE MID- AND UPPER-
LEVEL CIRCULATION AND BACK INTO SOUTHEASTERN MT THROUGH THE DAY. A
DRYING TREND COULD BEGIN IN SOUTH CENTRAL MT BY AFTERNOON...MAINLY
AWAY FROM UPSLOPE AREAS...AS FORECAST SOUNDINGS IN LOCALES SUCH AS
BILLINGS START SHOWING LESS SATURATION AFTER 18 UTC. IT COULD TAKE
UNTIL VERY LATE MON NIGHT OR EVEN INTO TUE THOUGH BEFORE DRYING IS
ABLE TO TAKE HOLD IN SOUTHEASTERN MT. LARGE LOWS LIKE THIS ONE ARE
OFTEN SLOWER TO MOVE THAN EXPECTED INITIALLY. THE RIDGE THAT FORMS
AT 500 HPA TO THE NORTH OF THE LOW IN SOUTHERN CANADA WILL PLAY A
BIG ROLE IN ITS SPEED SINCE IT WILL BE A BLOCKING MECHANISM.
SO...IN SUMMARY...THIS LOOKS INCREASINGLY LIKE A BIG RAIN EVENT IN
MUCH OF THE AREA. WHILE CONVECTIVE ELEMENTS WILL BE LESS LIKELY AS
WE GO FORWARD...THERE IS STILL ENSEMBLE SUPPORT FOR THREE AND SIX-
HOUR RAIN TOTALS OF A HALF INCH OR MORE IN MANY AREAS. WE CHOSE TO
ISSUE A FLASH FLOOD WATCH FOR THE BURN SCAR AREAS OF SOUTH CENTRAL
AND SOUTHEASTERN MT THROUGH 12 UTC TUE SINCE AMOUNTS LIKE THAT MAY
BE ENOUGH TO CAUSE ISSUES IN SOME OF THOSE AREAS. SCHULTZ
.LONG TERM...VALID FOR TUE...WED...THU...FRI...SAT...
CONTINUE TO SLOW THE TRANSITION TO DRIER WEATHER. MODELS
STRUGGLING WITH THE EXIT SPEED OF THE DEEP UPPER LOW CURRENTLY
PROVIDING GENEROUS PRECIPITATION TO THE FORECAST AREA. MODELS WERE
FAIRLY CONSISTENT NOW IN VERY SLOWLY SLIDING THE UPPER LOW
EASTWARD. DIFFERENCES CENTER ON THE POSITION OF THE BLOCKING HIGH
IN SOUTHERN CANADA. THE GFS WAS FARTHER SOUTH AND THUS CLEARS THE
FORECAST AREA WITH DYNAMICS SOONER THAN THE ECMWF ON TUESDAY. THE
ECMWF HAS THE BLOCKING HIGH FARTHER NORTH AND THUS LINGERS ENERGY
INTO TUESDAY OVER THE SOUTHEAST. WILL KEEP SCATTERED POPS IN THE
EAST ON TUESDAY WHILE THE WEST SHOULD EFFECTIVELY DRY OUT. LOWERED
HIGH TEMPERATURES AS THE UPPER RIDGE WAS NOT NEARLY AS AMPLIFIED
ON 00Z RUNS.
THE NEXT UPSTREAM...AND VERY DEEP...UPPER LOW OVER THE NORTHWEST
SLIDES INTO PLACE AND TURNS THE FLOW SOUTHERLY OVER SOUTHERN
MONTANA AND NORTHERN WYOMING BY WEDNESDAY. THIS WILL ESTABLISH LOW
LEVEL EASTERLY FLOW WITH LOWER SURFACE PRESSURES OVER THE GREAT
BASIN ALLOWING DEWPOINTS TO STAY UP. MODELS CONTINUE TO BACK OFF
WITH THE DRIER AIR ALOFT AND LINGER 700MB MOISTURE INTO FRIDAY NOW
AS THE UPPER LOW INCHES EASTWARD. WILL KEEP POPS MENTIONED FROM
WEDNESDAY ONWARD WITH THE BEST CHANCE OVER THE WEST CLOSER TOO THE
UPPER LOW AND UNDER THE INFLUENCE OF SLIGHTLY COOLER AIR ALOFT.
THE ECMWF WAS A LITTLE FASTER IN KICKING THE UPPER LOW NORTHEAST
ON FRIDAY BUT BOTH MODELS HAVE THE STRONGEST DYNAMICS HEADED NORTH
OF THE FORECAST AREA...SO DID NOT GO THAT HIGH WITH POPS FRIDAY
AND SATURDAY. OVERALL...COOLED THINGS DOWN A LITTLE BIT THROUGHOUT
THE EXTENDED WITH A LESS AMPLIFIED RIDGE NOW ADVERTISED BETWEEN
THE TWO DEEP UPPER LOWS. TWH
&&
.AVIATION...
ACTIVE WEATHER WILL CONTINUE TODAY AS AN AREA OF LOW PRESSURE
ALOFT MOVES SLOWLY THROUGH THE REGION. EXPECT SHOWERS AND ISOLATED
THUNDERSTORMS TODAY...WITH AREAS OF MVFR TO IFR CONDITIONS. SOME
FOG IS ALSO POSSIBLE EARLY THIS MORNING DUE TO THE ABUNDANT
SURFACE MOISTURE IN PLACE. FOG MAY REDUCE FLIGHT CONDITIONS TO IFR
OR LOWER IF IT DEVELOPS...AND THIS IS MOST LIKELY TO OCCUR IS IN
EASTERN PARTS NEAR KMLS AND KBHK. MOUNTAINS WILL BE OBSCURED. TWH
&&
.PRELIMINARY POINT TEMP/POPS...
TDY MON TUE WED THU FRI SAT
-------------------------------------------------------
BIL 058 049/061 045/069 046/069 049/072 049/074 050/075
+/T +8/R 41/B 12/T 42/T 22/T 22/T
LVM 056 046/058 038/065 040/067 040/067 041/069 042/069
7/T 86/R 41/B 14/T 44/T 43/T 33/T
HDN 059 050/061 045/070 044/071 049/074 048/077 050/077
+/T ++/R 51/E 12/T 32/T 22/T 22/T
MLS 059 051/060 046/064 046/068 050/071 050/074 052/076
+/T ++/R 53/W 12/T 22/T 22/T 22/T
4BQ 059 049/057 044/062 044/068 048/072 049/074 051/076
+/T ++/R 64/W 22/T 22/T 22/T 22/T
BHK 059 049/057 043/058 044/064 047/067 048/070 051/074
+/T ++/R 84/W 22/T 22/T 22/T 22/T
SHR 055 047/056 042/062 040/069 046/072 046/075 048/075
+/T ++/R 52/W 12/T 32/T 22/T 22/T
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...FLASH FLOOD WATCH IN EFFECT THROUGH LATE MONDAY NIGHT FOR
ZONES 29>31-36>38-57-58.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
000
FXUS65 KTFX 190455
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1055 PM MDT Sat May 18 2013
...UPDATE TO AVIATION...
.DISCUSSION...
Update forthcoming. Showers and isolated weak thunderstorms continue
across the area. No reports of severe criteria with only very small
hail reported with some storms. HRRR analysis and latest RUC model
indicating a lessening of shower activity after 06z and, have
lowered pops a bit for that period. Remainder of forecast looks on
track with unsettled showery pattern continuing through Sunday.
Emanuel
&&
.AVIATION...
UPDATED 0500Z.
Unsettled weather continues for the next 24 hours as rain showers
are expected to remain in the area for the entire TAF period. An
isolated thunderstorm is still possible...however not expecting any
long duration impacts so no VCTS or TSRA in the TAFs. Ceilings and
visibilities should remain VFR but brief MVFR/IFR conditions are
possible near any precipitation areas. Suk
&&
.PREV DISCUSSION...Issued 257 PM MDT Sat May 18 2013
Tonight through Monday...Scattered showers and isolated
thunderstorms are developing this afternoon as instability
increases with an upper-level trough pushing through the Northern
Rockies. With the cooler air aloft, some of these showers and
thunderstorms may contain graupel. On Sunday, the upper-level low
associated with the trough will further deepen as it moves into
eastern Montana, which will shift the surface flow more northerly.
As abundant moisture wraps into this system, upslope precipitation
will develop and become steadier and more widespread, especially
during the afternoon hours. There are still some differences in
the models regarding where the heaviest precipitation will be
located, however confidence is increasing that the best precip
chances will be for areas along and east of I-15 as well as areas
along the Rocky Mountain Front. Cooler, Canadian air will also
keep snow levels lower on Sunday with snow levels between 7000 and
8000 feet. Over southwest Montana, precipitation will be
widespread but off and on through the period. The system will move
further east on Monday with drier air pushing in west to east.
High temperatures will remain below average through Sunday, then
rise to near seasonal averages on Monday. MLV
Monday Night through Saturday...Extended forecast period begins with
mostly quiet conditions as the upper level system that will cross
Montana this weekend will be moving into the Upper Midwest states
and a well-amplified high pressure ridge begins to settle in over
ern Montana and the Dakotas. Meanwhile, a second upper level trof
is forecast to swing through western Canada and form a closed low
pressure center over the PACNW coast by Tues eve. With the large
ridge remaining anchored thru the middle of the country, the Pacific
low essentially becomes stationary, drifting along the coast and
occasionally moving inland during the latter half of next week.
Minor shortwaves and accompanying moisture rotating around the
central low will bring intermittent periods of showers and isolated
thunderstorms each day from Wed onward. Forecast models are in
decent agreement that most parts of central/southwest MT will see
rain during this time, but precip amounts still look to be generally
light (0.10-0.15 inch or less) over the plains and valleys.
Rainfall totals are slightly higher (0.20-0.50 inch) over the
melting snowfields of the Rocky Mtn Front and Little Belt Mtns,
which gives concern for increased streamflows in creeks/rivers in
those areas. Persistent southerly flow aloft will allow
temperatures to stay close to typical seasonal values with highs in
the mid-60s to the low 70s each day, though that will be modified
quite a bit by a fair amount of cloud cover and the timing of the
shortwave passages.
Waranauskas
&&
.HYDROLOGY...
Two upper level trofs, one moving through our region this weekend
and the other becoming stationary over the PACNW coast for much of
next week, will bring increased chances for rainfall over the next
several days. Though cooler temperatures will reduce snowmelt
slightly, the primary concern is that rain on the melting snowpack
will cause enhanced rises in stream/river levels. Most area rivers
are currently well below flood stage but a handful of sites are near
or approaching bankfull, so rainfall totals and river stage
forecasts will be closely monitored for significant changes and
impacts. Waranauskas
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 44 61 44 66 / 60 70 60 40
CTB 42 62 42 67 / 60 50 40 30
HLN 44 62 45 68 / 60 50 50 30
BZN 41 60 41 66 / 80 60 50 30
WEY 36 53 35 59 / 70 60 50 40
DLN 38 59 40 66 / 60 50 40 20
HVR 47 68 46 71 / 80 80 70 70
LWT 44 57 43 62 / 80 80 70 60
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
weather.gov/greatfalls
000
FXUS65 KBYZ 190336
AFDBYZ
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
936 PM MDT SAT MAY 18 2013
.UPDATE...
LARGE TROUGH OVER THE INTERMOUNTAIN REGION AND HIGH PLAINS.
MODEST QG FORCING LINGERS OVER OUR WEST TONIGHT. BEST ENVIRONMENT
FOR STORMS FROM OUR EASTERN BORDER INTO THE DAKOTAS WHERE SHEAR
AND MOISTURE CONVERGENCE HAVE COMBINED. STORM NEAR OLLIE JUST ON
THE CUSP OF THAT ENVIRONMENT GENERATED GOLFBALL SIZE HAIL THIS
EVENING. I DROPPED POPS DOWN BELOW CATEGORICAL LEVELS OVERNIGHT.
AS CUT OFF UPPER LOW DEVELOPS OVER EASTERN WYOMING TONIGHT IT WILL
ROTATE WAVES OF VORTICITY INTO EASTERN MONTANA AND NORTHERN
WYOMING SUNDAY. SO WE EXPECT ANOTHER RAINY DAY. BT
&&
.SHORT TERM...VALID FOR SUN AND MON...
DEEP UPPER TROUGH OF LOW PRESSURE HAS BROUGHT SOME MUCH NEEDED
PRECIPITATION TO THE ENTIRE FORECAST AREA. THE TROUGH WILL MOVE
SLOWLY ACROSS THE AREA AND THE COOL AND WET TREND WILL CONTINUE
TONIGHT THROUGH MONDAY.
TONIGHT...SHOWERS AND THUNDERSTORMS WILL CONTINUE OVER MOST OF
THE AREA TONIGHT AS A JET SPEED MAX AND STRONG VORTICITY MOVES
ACROSS THE AREA. RAINFALL HAS BEEN HEAVY AT TIMES TODAY AND THIS
TREND WILL CONTINUE OVERNIGHT. A FEW STRONG THUNDERSTORMS MAY BE
POSSIBLE OVER EXTREME SOUTHEAST MONTANA THIS EVENING AS SURFACE
BASED CAPES PROGGED AROUND 1200 J/KG AND LI`S NEAR -4C. SURFACE
TROUGH OVER THIS AREA WILL PROVIDE GOOD SURFACE CONVERGENCE ALONG
WITH INCREASING SHEAR ALOFT. THESE FACTORS WILL AID IN THE
DEVELOPMENT OF A FEW STRONG THUNDERSTORMS OVER SOUTHERN CARTER
COUNTY THIS EVENING. THE MAIN THREAT FROM STORMS THIS EVENING WILL
BE HEAVY RAINS AS PW`S ARE AROUND 1 INCH. UPPER FORCING WILL
DIMINISH BY LATE EVENING BUT HAVE STILL CONTINUED LIKELY POPS
ACROSS THE ENTIRE AREA. FOG WILL ALSO BE POSSIBLE AFTER 06Z
TONIGHT AS LOW LEVELS WILL BE SATURATED ALONG WITH LIGHT WINDS.
SUNDAY THROUGH MONDAY...SOME DISCREPANCIES STILL EXIST WITH THE
MODELS PLACEMENT OF A DEVELOPING CLOSED UPPER LOW SUNDAY. THE
POSITIONING OF THIS LOW WILL DETERMINE HOW MUCH ADDITIONAL QPF WE
WILL RECEIVE. THE UPPER LOW WILL WRAP ENERGY BACK INTO OUR AREA
DURING THIS TIME PERIOD SO WILL CONTINUE HIGH POPS FOR NOW WITH
SOME UNCERTAINTY OF WHERE THE HEAVIEST RAINFALL WILL SETUP. THE
BEST CHANCE FOR SIGNIFICANT PRECIPITATION LOOKS TO BE OVER OUR
EASTERN ZONES WITH STRONG UPSLOPE FLOW BRINGING DECENT RAINFALL TO
OUR UPSLOPE AREAS ALONG THE FOOTHILLS AS WELL AS THE NORTHEAST BIG
HORN MOUNTAINS. WE COULD SEE AN ADDITIONA 1 TO 2 INCHES OF
PRECIPITATION ACROSS THE ENTIRE FORECAST AREA BEFORE THIS STORM
SYSTEM MOVES OUT OF THE AREA MONDAY NIGHT. LOOK FOR TEMPERATURES
TO RUN 10 TO 20 DEGREES BELOW SEASONAL NORMALS SUNDAY AND MONDAY.
RICHMOND
.LONG TERM...VALID FOR TUE...WED...THU...FRI...SAT...
MINIMAL CHANGES FOR THE EXTENDED PERIOD AT THIS TIME...AS SOME
DISCREPANCY IN MODELS REMAIN THROUGH PERIOD AS TO DETAILS.
HOWEVER THE OVERALL PATTERN REMAIN PRETTY COMPARABLE. TEMPERATURES
THROUGH THE PERIOD WILL BE ON THE RISE...WITH AROUND NORMAL
TEMPERATURES EXPECTED FOR TUESDAY AND WEDNESDAY...AND A FEW
DEGREES ABOVE NORMAL THEREAFTER.
SOME DEGREE OF RIDGING IS PROGGED TO DEVELOP ACROSS THE
REGION...BETWEEN SYSTEMS...BEGINNING TUESDAY. THE CURRENT
WEATHER SYSTEM ACTS AS A BLOCKING FEATURE IN THE EAST HOLDING UP
THE PROGRESSION OF THE NEXT SYSTEM. SOUTHWEST FLOW AHEAD OF THE
THE LOW CENTERED OVER NORTHWESTERN WASHINGTON BY WEDNESDAY
NIGHT...AND SENDS A SIGNIFICANT SHORTWAVE ACROSS THE REGION
OVERNIGHT. GFS IS MUCH DRIER THAN THE EC WITH THIS SYSTEM...BUT
CAN SEE SOME POTENTIAL WITH HEATING...SHORTWAVE...AND POSSIBLE TAP
INTO GULF MOISTURE SETTING UP. SOUTHWEST FLOW REMAINS IN
PLACE...BUT APPEARS TO TAP IN TO DRY AIR ALOFT FOLLOWING THIS
WAVE...HOWEVER THERE CONTINUES TO BE SOME INDICATION OF A GULF
MOISTURE TAP AT THE SURFACE THROUGH THE REMAINDER OF THE EXTENDED
PERIOD. SFC MOISTURE FROM RECENT RAINS AND POSSIBLE GULF MOISTURE
INFLUX...COMBINED WITH DAYTIME HEATING AND LIKELY WEAK SHORTWAVES
RADIATING THROUGH THE FLOW SHOULD ALLOW FOR AT LEAST ISOLATED
THUNDER POTENTIAL IN THE AFTERNOON...AND POSSIBLE REMNANT SHOWERS
INTO THE OVERNIGHT HOURS. KEPT INHERITED POPS IN PLACE...BUT
SPREAD SLIGHT POPS ACROSS THE PLAINS THROUGH THE LATTER HALF OF
THE EXTENDED PERIOD. AAG
&&
.AVIATION...
STRONG THUNDERSTORMS WITH LOCALIZED HEAVY RAIN AND HAIL NEAR
BAKER AND EKALAKA AT 03Z WILL MOVE INTO THE DAKOTAS BY 04Z. THIS
WILL END THE THREAT OF STRONG THUNDERSTORMS.
ACTIVE WEATHER WILL CONTINUE THROUGH TOMORROW AS AN AREA OF LOW
PRESSURE ALOFT MOVES SLOWLY THROUGH THE REGION. EXPECT SHOWERS AND
ISOLATED THUNDERSTORMS TONIGHT AND SUNDAY...WITH AREAS OF MVFR TO
IFR CONDITIONS. SOME FOG IS ALSO POSSIBLE TONIGHT DUE TO THE
ABUNDANT SURFACE MOISTURE IN PLACE. FOG MAY REDUCE FLIGHT
CONDITIONS TO IFR OR LOWER IF IT DEVELOPS...AND THIS IS MOST
LIKELY TO OCCUR IN EASTERN PARTS NEAR KMLS AND KBHK. MOUNTAINS
WILL BE ALMOST PERMANENTLY OBSCURED OVER THE NEXT 24 HOURS.
JKL
&&
.PRELIMINARY POINT TEMP/POPS...
SUN MON TUE WED THU FRI SAT
-----------------------------------------------------------
BIL 049/058 048/062 044/071 047/072 049/073 049/076 050/076
48/T 86/W 31/B 12/T 42/T 22/T 22/T
LVM 045/057 040/059 037/067 041/072 040/069 041/071 042/071
47/T 85/W 31/B 14/T 43/T 33/T 33/T
HDN 051/062 047/062 045/071 045/074 049/076 048/078 049/078
38/T 86/W 31/E 12/T 32/T 22/T 22/T
MLS 051/063 049/062 046/068 046/072 050/073 048/075 051/076
38/T 86/W 53/W 22/T 22/T 22/T 22/T
4BQ 051/059 047/060 044/065 044/072 048/073 047/075 050/076
28/T 87/W 53/W 11/B 22/T 22/T 22/T
BHK 048/060 047/060 043/062 043/068 048/069 048/073 050/076
78/T 87/W 63/W 21/B 22/T 22/T 22/T
SHR 045/056 043/057 041/065 040/074 046/074 045/076 047/076
27/T 87/W 42/W 12/T 32/T 22/T 22/T
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
000
FXUS65 KGGW 190331
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
931 PM MDT SAT MAY 18 2013
.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH MONDAY...
UPDATE...SHOWERS AND THUNDERSTORMS ARE CONTINUING TO AFFECT THE
CWA THIS EVENING. A FAIRLY CONCENTRATED AREA OF SHOWERS AND
THUNDERSTORMS PRODUCING HEAVY RAINFALL HAVE BEEN DRIFTING VERY
SLOWLY SOUTHEASTWARD ACROSS SOUTHERN MCCONE COUNTY. THIS PROMPTED
THE ISSUANCE OF A FLOOD ADVISORY THROUGH 11PM FOR POOR POOR DRAINAGE
AREAS NEAR HIGHWAYS 200 AND 253 NEAR BROCKWAY. IN FACT...A COUPLE OF
CALLS HAVE COME IN THIS EVENING DESCRIBING SOME FLOODING ON
HIGHWAY 253 NEAR BROCKWAY.
LATEST HRRR GUIDANCE HAS SHOWER AND THUNDERSTORM ACTIVITY
DIMINISHING SOME AS IT LIFTS NORTHWARD...BUT ALSO DEPICTS SOME
REDEVELOPMENT ACROSS SOME OF THE WESTERN PORTIONS OF THE CWA. THIS
HAS SOME SUPPORT FROM THE LATEST NAM AND THE 12Z ECMWF AS WELL SO
INCREASED POPS OVERNIGHT IN THESE AREAS. BUFKIT SOUNDINGS SHOWS
TOTAL TOTALS AROUND 50 AND LI BETWEEN 0 AND -1 FOR A LOT OF THE
CWA AROUND 06Z AND SO INCLUDED A MENTION OF THUNDER FOR THE REST
OF THE OVERNIGHT AS WELL. MALIAWCO
PREVIOUS SHORT TERM DISCUSSION...
A LARGE TROUGH HAS DUG IN OVER THE SOUTH WEST CONUS WITH A RIDGE
OVER WESTERN CANADA. VARIABLE IMPULSES OF ENERGY MOVING UP FROM
THE DOWNSTREAM PART OF THE SOUTHERN TROUGH WILL SUPPORT CONTINUED
PRECIPITATION THROUGH MONDAY AFTERNOON. RAINFALL IS ALSO SUPPORTED
BY A SURFACE LOW SOUTHEAST OF MONTANA THAT IS DRAWING LOW LEVEL
MOISTURE INTO THE AREA.
SYSTEM CONTINUES TO STRENGTHEN AND GRADUALLY MOVE EASTWARD...WITH
THE EFFECTS EXITING NORTHEAST MONTANA MONDAY NIGHT. ON
MONDAY...MOST OF THE MODELS HAVE MOST OF THE PRECIPITATION TO THE
SOUTHEAST PART OF THE CWA...BUT WITH POTENTIALLY HIGHER AMOUNTS
THAN EARLIER IN THE FORECAST. SOUNDINGS ARE VERY SATURATED WITH
AROUND AN INCH OF PRECIPITABLE WATER..LEADING TO THE FORECAST OF
MOSTLY RAIN SHOWERS. SOME INSTABILITY IN THE SOUNDINGS WILL LEAD
TO SOME LIMITED THUNDERSTORM ACTIVITY. THUNDERSTORMS ARE LIMITED
BY THE LACK OF CAP...WHICH WILL NOT ALLOW MUCH BUILD-UP OF
CONVECTIVE ENERGY. WINDS WILL PICK A LITTLE FROM THE NORTH ON
SUNDAY AS THE SURFACE LOW TIGHTENS...HOWEVER...THEY SHOULD STAY
BELOW 20KTS...WITH LOCALLY HIGHER GUSTS POSSIBLE IN OUTFLOW AREAS. MARTIN
.LONG TERM...MONDAY NIGHT THROUGH SATURDAY...
THE ONLY CHANGES IN THE SHORT TERM LOOK TO BE STRONGER WINDS
THURSDAY AND THE POSSIBILITY FOR A SEVERE EVENT OR TWO AT THE END
OF THE PERIOD.
THE GFS WANTS TO RAMP UP WINDS QUITE A BIT THURSDAY AFTERNOON WITH
850 WINDS OVER THE CWA APPROACHING 50 KNOTS AS A MID LEVEL HIGH
OVER THE MINNESOTA AND ONTARIO REGION BATTLES WITH THE APPROACHING
PACIFIC NORTHWEST LOW. THE ECMWF HAS A BIT LESS AMPLIFIED GRADIENT
AND THUS A THINNER BAND OF STRONG 850 WINDS OVER THE CWA...BUT HAS
A SIMILAR UPPER PATTERN AS GFS. WENT CLOSER TO THE ECMWF SOLUTION
AS THE GFS TENDS TO HAVE WINDS A BIT HIGH OVER THE AREA.
AS THE UPPER LOW APPROACHES FOR THE WEEKEND...LOBES OF SHORTWAVE
ENERGY MAY CONTINUE TO BRING CHANCES FOR THUNDERSTORM DEVELOPMENT.
SATURDAY AFTERNOON HAS THE GFS AND ECMWF PUTTING OUT OVER 2000
J/KG OF CAPE OVER PARTS OF THE AREA...SO THERE WILL BE PLENTY OF
INSTABILITY OVER THE REGION. SUNDAY AFTERNOON AND EVENING SHOWS ROUGHLY
THE SAME SCENARIO...AND EVEN DIPS INTO MONDAY AS THE LOW SLOWLY
PROGRESSES NORTHWARD OFF TO OUR WEST AND NORTHWEST. THIS WILL
PROVIDE BROAD SOUTHWEST FLOW ALOFT FOR THE WEEKEND...WHICH SHOULD
GIVE ENOUGH UPPER LEVEL SUPPORT WITH DIFLUENT FLOW COMBINED WITH
LOBES OF SHORTWAVE ENERGY OFF THE MAIN FLOW...ESPECIALLY FOR
SATURDAY. FOR NOW...THE GFS HAS A WARM FRONT PASS THROUGH THE CWA
FRIDAY...AND THE ECMWF HAS ONE PASS SATURDAY. MORE MODEL AGREEMENT
ON TIMING WILL SHOW IF WE GET OUR FIRST SIGNIFICANT ROUND OF
STORMS THIS SEASON NEXT WEEKEND. BARNWELL
PREVIOUS LONG TERM DISCUSSION...THE EXTENDED FORECAST BEGINS
MONDAY NIGHT WITH AN UPPER LOW EXITING INTO THE UPPER MISSISSIPPI
RIVER VALLEY AND WEAK RIDGING BUILDING INTO NORTHEASTERN MONTANA.
BY WEDNESDAY MORNING ANOTHER UPPER LOW MOVES IN OVER THE PACIFIC
NORTHWEST SETTING UP DI-FLUENT SOUTHWEST FLOW ALOFT OVER THE AREA
THROUGH THE END OF THE EXTENDED.
THIS WILL CONTINUE THE COOLISH TEMPERATURES DURING THE DAY AND
NEAR NORMAL TEMPERATURES AT NIGHT. PRECIPITATION CHANCES SHOULD
RANGE SLIGHTLY ABOVE NORMAL... HOWEVER PIN POINTING ANY BETTER
DAYS THAN OTHERS WILL BE VERY HARD.
ENSEMBLES OF THE GFS AND EC SHOW HIGH CONFIDENCE IN AN UPPER LOW
OVER THE PACIFIC NORTHWEST...HOWEVER DO HAVE TROUBLE KEEPING THE
DAY TO DAY PLACEMENT OF THE UPPER LOW THE SAME. RMOP IS PRETTY
GOOD FOR UPPER LOWS OVER THE PACIFIC NORTHWEST. MODERATE TO HIGH
CONFIDENCE ON THE PATTERN. HOWEVER THE PATTERN IS MORE SHOWERY IN
NATURE NOT ALLOWING FOR THE CONFIDENCE TO DOUBLE OF CLIMO POPS AT
THIS TIME. PROTON
&&
.AVIATION...
VFR CONDITIONS ARE EXPECTED TO DETERIORATE TO MVFR AND POSSIBLY IFR
FOR KGDV AND KSDY LATER TONIGHT AS AN AREA OF SHOWERS AND
THUNDERSTORMS MOVE NORTHEAST INTO THESE AREAS. BETTER CONDITIONS
ARE EXPECTED FOR KGGW AND KOLF WHERE LIGHTER RAINS ARE EXPECTED
TONIGHT.
SINCE KOLF ASOS IS NOT TRANSMITTING..WE HAVE TAGGED THE TAF WITH
AMD NOT SKED. JAMBA
&&
.HYDROLOGY...
THE NEXT FEW DAYS WILL BE RATHER WET AS AN UPPER-LEVEL TROUGH
AFFECTS THE AREA. SEVERAL DISTURBANCES ASSOCIATED WITH THIS TROUGH
WILL PASS THROUGH WHICH WILL KEEP CHANCES FOR RAIN WITH SOME
THUNDERSTORMS THROUGH EARLY NEXT WEEK. MODEL GUIDANCE DEPICTS HIGH
AMOUNTS OF MOISTURE WITH THIS SYSTEM. AT THIS POINT THE
ENVIRONMENT LOOKS FAVORABLE FOR SLOW-MOVING STORMS WITH HIGHER
PRECIPITATION IN LOCALIZED AREAS.
MOST OF THE BASINS IN NORTHEAST MONTANA WILL BE ABLE TO ACCOMMODATE
THIS AMOUNT OF MOISTURE... AT LEAST EARLY ON IN THE EVENT. THERE IS
SOME CONCERN FOR RAPIDLY RISING STREAMS...FIELD FLOODING AND
LOCALIZED FLOODING IN TOWNS AS THE EVENT PERSISTS. SOME MINOR
FLOODING MAY BECOME AN ISSUE... ESPECIALLY FOR THE AREAS FROM
GLASGOW TO CIRLE AND EASTWARD INTO NORTH DAKOTA WHERE THE POTENTIAL
FOR STRONGER THUNDERSTORMS IS HIGHER.
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
WEATHER.GOV/GLASGOW
000
FXUS65 KTFX 190314
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
855 PM MDT Sat May 18 2013
.DISCUSSION...
Update forthcoming. Showers and isolated weak thunderstorms continue
across the area. No reports of severe criteria with only very small
hail reorted with some storms. HRRR analysis and latest RUC model
indicating a lessening of shower activity after 06z and, have
lowered pops a bit for that period. Remainder of forecast looks on
track with unsettled showery pattern continuing through Sunday.
Emanuel
&&
.AVIATION...
UPDATED 00Z.
Unsettled weather continues for the next 24 hours as rain showers
are expected to remain in the area for the entire TAF period. An
isolated thunderstorm will be possible until sunset...however not
expecting any long duration impacts so no VCTS or TSRA in the TAFs.
Ceilings and visibilities should remain VFR but brief MVFR/IFR
conditions are possible near any precipitation areas. Suk
&&
.PREV DISCUSSION...Issued 257 PM MDT Sat May 18 2013
Tonight through Monday...Scattered showers and isolated
thunderstorms are developing this afternoon as instability
increases with an upper-level trough pushing through the Northern
Rockies. With the cooler air aloft, some of these showers and
thunderstorms may contain graupel. On Sunday, the upper-level low
associated with the trough will further deepen as it moves into
eastern Montana, which will shift the surface flow more northerly.
As abundant moisture wraps into this system, upslope precipitation
will develop and become steadier and more widespread, especially
during the afternoon hours. There are still some differences in
the models regarding where the heaviest precipitation will be
located, however confidence is increasing that the best precip
chances will be for areas along and east of I-15 as well as areas
along the Rocky Mountain Front. Cooler, Canadian air will also
keep snow levels lower on Sunday with snow levels between 7000 and
8000 feet. Over southwest Montana, precipitation will be
widespread but off and on through the period. The system will move
further east on Monday with drier air pushing in west to east.
High temperatures will remain below average through Sunday, then
rise to near seasonal averages on Monday. MLV
Monday Night through Saturday...Extended forecast period begins with
mostly quiet conditions as the upper level system that will cross
Montana this weekend will be moving into the Upper Midwest states
and a well-amplified high pressure ridge begins to settle in over
ern Montana and the Dakotas. Meanwhile, a second upper level trof
is forecast to swing through western Canada and form a closed low
pressure center over the PACNW coast by Tues eve. With the large
ridge remaining anchored thru the middle of the country, the Pacific
low essentially becomes stationary, drifting along the coast and
occasionally moving inland during the latter half of next week.
Minor shortwaves and accompanying moisture rotating around the
central low will bring intermittent periods of showers and isolated
thunderstorms each day from Wed onward. Forecast models are in
decent agreement that most parts of central/southwest MT will see
rain during this time, but precip amounts still look to be generally
light (0.10-0.15 inch or less) over the plains and valleys.
Rainfall totals are slightly higher (0.20-0.50 inch) over the
melting snowfields of the Rocky Mtn Front and Little Belt Mtns,
which gives concern for increased streamflows in creeks/rivers in
those areas. Persistent southerly flow aloft will allow
temperatures to stay close to typical seasonal values with highs in
the mid-60s to the low 70s each day, though that will be modified
quite a bit by a fair amount of cloud cover and the timing of the
shortwave passages.
Waranauskas
&&
.HYDROLOGY...
Two upper level trofs, one moving through our region this weekend
and the other becoming stationary over the PACNW coast for much of
next week, will bring increased chances for rainfall over the next
several days. Though cooler temperatures will reduce snowmelt
slightly, the primary concern is that rain on the melting snowpack
will cause enhanced rises in stream/river levels. Most area rivers
are currently well below flood stage but a handful of sites are near
or approaching bankfull, so rainfall totals and river stage
forecasts will be closely monitored for significant changes and
impacts. Waranauskas
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 44 61 44 66 / 60 70 60 40
CTB 42 62 42 67 / 60 50 40 30
HLN 44 62 45 68 / 60 50 50 30
BZN 41 60 41 66 / 80 60 50 30
WEY 36 53 35 59 / 70 60 50 40
DLN 38 59 40 66 / 60 50 40 20
HVR 47 68 46 71 / 80 80 70 70
LWT 44 57 43 62 / 80 80 70 60
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
weather.gov/greatfalls
000
FXUS65 KBYZ 190146
AFDBYZ
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
746 PM MDT SAT MAY 18 2013
.UPDATE...
QUICK UPDATE TO ADJUST WIND AND POPS FOR CURRENT RADAR TRENDS AND
UPSTREAM OBSERVATIONS. WILL ISSUE ANOTHER UPDATE BY 930 PM. BT
&&
.SHORT TERM...VALID FOR SUN AND MON...
DEEP UPPER TROUGH OF LOW PRESSURE HAS BROUGHT SOME MUCH NEEDED
PRECIPITATION TO THE ENTIRE FORECAST AREA. THE TROUGH WILL MOVE
SLOWLY ACROSS THE AREA AND THE COOL AND WET TREND WILL CONTINUE
TONIGHT THROUGH MONDAY.
TONIGHT...SHOWERS AND THUNDERSTORMS WILL CONTINUE OVER MOST OF
THE AREA TONIGHT AS A JET SPEED MAX AND STRONG VORTICITY MOVES
ACROSS THE AREA. RAINFALL HAS BEEN HEAVY AT TIMES TODAY AND THIS
TREND WILL CONTINUE OVERNIGHT. A FEW STRONG THUNDERSTORMS MAY BE
POSSIBLE OVER EXTREME SOUTHEAST MONTANA THIS EVENING AS SURFACE
BASED CAPES PROGGED AROUND 1200 J/KG AND LI`S NEAR -4C. SURFACE
TROUGH OVER THIS AREA WILL PROVIDE GOOD SURFACE CONVERGENCE ALONG
WITH INCREASING SHEAR ALOFT. THESE FACTORS WILL AID IN THE
DEVELOPMENT OF A FEW STRONG THUNDERSTORMS OVER SOUTHERN CARTER
COUNTY THIS EVENING. THE MAIN THREAT FROM STORMS THIS EVENING WILL
BE HEAVY RAINS AS PW`S ARE AROUND 1 INCH. UPPER FORCING WILL
DIMINISH BY LATE EVENING BUT HAVE STILL CONTINUED LIKELY POPS
ACROSS THE ENTIRE AREA. FOG WILL ALSO BE POSSIBLE AFTER 06Z
TONIGHT AS LOW LEVELS WILL BE SATURATED ALONG WITH LIGHT WINDS.
SUNDAY THROUGH MONDAY...SOME DISCREPANCIES STILL EXIST WITH THE
MODELS PLACEMENT OF A DEVELOPING CLOSED UPPER LOW SUNDAY. THE
POSITIONING OF THIS LOW WILL DETERMINE HOW MUCH ADDITIONAL QPF WE
WILL RECEIVE. THE UPPER LOW WILL WRAP ENERGY BACK INTO OUR AREA
DURING THIS TIME PERIOD SO WILL CONTINUE HIGH POPS FOR NOW WITH
SOME UNCERTAINTY OF WHERE THE HEAVIEST RAINFALL WILL SETUP. THE
BEST CHANCE FOR SIGNIFICANT PRECIPITATION LOOKS TO BE OVER OUR
EASTERN ZONES WITH STRONG UPSLOPE FLOW BRINGING DECENT RAINFALL TO
OUR UPSLOPE AREAS ALONG THE FOOTHILLS AS WELL AS THE NORTHEAST BIG
HORN MOUNTAINS. WE COULD SEE AN ADDITIONA 1 TO 2 INCHES OF
PRECIPITATION ACROSS THE ENTIRE FORECAST AREA BEFORE THIS STORM
SYSTEM MOVES OUT OF THE AREA MONDAY NIGHT. LOOK FOR TEMPERATURES
TO RUN 10 TO 20 DEGREES BELOW SEASONAL NORMALS SUNDAY AND MONDAY.
RICHMOND
.LONG TERM...VALID FOR TUE...WED...THU...FRI...SAT...
MINIMAL CHANGES FOR THE EXTENDED PERIOD AT THIS TIME...AS SOME
DISCREPANCY IN MODELS REMAIN THROUGH PERIOD AS TO DETAILS.
HOWEVER THE OVERALL PATTERN REMAIN PRETTY COMPARABLE. TEMPERATURES
THROUGH THE PERIOD WILL BE ON THE RISE...WITH AROUND NORMAL
TEMPERATURES EXPECTED FOR TUESDAY AND WEDNESDAY...AND A FEW
DEGREES ABOVE NORMAL THEREAFTER.
SOME DEGREE OF RIDGING IS PROGGED TO DEVELOP ACROSS THE
REGION...BETWEEN SYSTEMS...BEGINNING TUESDAY. THE CURRENT
WEATHER SYSTEM ACTS AS A BLOCKING FEATURE IN THE EAST HOLDING UP
THE PROGRESSION OF THE NEXT SYSTEM. SOUTHWEST FLOW AHEAD OF THE
THE LOW CENTERED OVER NORTHWESTERN WASHINGTON BY WEDNESDAY
NIGHT...AND SENDS A SIGNIFICANT SHORTWAVE ACROSS THE REGION
OVERNIGHT. GFS IS MUCH DRIER THAN THE EC WITH THIS SYSTEM...BUT
CAN SEE SOME POTENTIAL WITH HEATING...SHORTWAVE...AND POSSIBLE TAP
INTO GULF MOISTURE SETTING UP. SOUTHWEST FLOW REMAINS IN
PLACE...BUT APPEARS TO TAP IN TO DRY AIR ALOFT FOLLOWING THIS
WAVE...HOWEVER THERE CONTINUES TO BE SOME INDICATION OF A GULF
MOISTURE TAP AT THE SURFACE THROUGH THE REMAINDER OF THE EXTENDED
PERIOD. SFC MOISTURE FROM RECENT RAINS AND POSSIBLE GULF MOISTURE
INFLUX...COMBINED WITH DAYTIME HEATING AND LIKELY WEAK SHORTWAVES
RADIATING THROUGH THE FLOW SHOULD ALLOW FOR AT LEAST ISOLATED
THUNDER POTENTIAL IN THE AFTERNOON...AND POSSIBLE REMNANT SHOWERS
INTO THE OVERNIGHT HOURS. KEPT INHERITED POPS IN PLACE...BUT
SPREAD SLIGHT POPS ACROSS THE PLAINS THROUGH THE LATTER HALF OF
THE EXTENDED PERIOD. AAG
&&
.AVIATION...
SHOWERS AND THUNDERSTORMS CONTINUE TO BECOME INCREASINGLY
WIDESPREAD...IMPACTING MUCH OF THE REGION WEST OF KMLS. SHOWERS
AND THUNDERSTORMS ARE EXPECTED TO SHIFT FURTHER EAST AND
NORTHEAST THROUGHOUT EVENING...AND PERSIST OVERNIGHT AND THROUGH
SUNDAY. SOME OF THE STORMS WILL CONTAIN MODERATE TO BRIEFLY HEAVY
RAINFALL AND COULD LOWER CONDITIONS TO MVFR/IFR. MOUNTAINS WILL BE
OBSCURED IN SHOWERS AND CLOUDS THROUGHOUT THE DAY. AAG
&&
.PRELIMINARY POINT TEMP/POPS...
SUN MON TUE WED THU FRI SAT
-----------------------------------------------------------
BIL 049/058 048/062 044/071 047/072 049/073 049/076 050/076
48/T 86/W 31/B 12/T 42/T 22/T 22/T
LVM 045/057 040/059 037/067 041/072 040/069 041/071 042/071
77/T 85/W 31/B 14/T 43/T 33/T 33/T
HDN 051/062 047/062 045/071 045/074 049/076 048/078 049/078
48/T 86/W 31/E 12/T 32/T 22/T 22/T
MLS 051/063 049/062 046/068 046/072 050/073 048/075 051/076
48/T 86/W 53/W 22/T 22/T 22/T 22/T
4BQ 051/059 047/060 044/065 044/072 048/073 047/075 050/076
48/T 87/W 53/W 11/B 22/T 22/T 22/T
BHK 048/060 047/060 043/062 043/068 048/069 048/073 050/076
88/T 87/W 63/W 21/B 22/T 22/T 22/T
SHR 045/056 043/057 041/065 040/074 046/074 045/076 047/076
47/T 87/W 42/W 12/T 32/T 22/T 22/T
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
000
FXUS65 KTFX 190003
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
603 PM MDT Sat May 18 2013
...UPDATE TO AVIATION...
.DISCUSSION...
Tonight through Monday...Scattered showers and isolated
thunderstorms are developing this afternoon as instability
increases with an upper-level trough pushing through the Northern
Rockies. With the cooler air aloft, some of these showers and
thunderstorms may contain graupel. On Sunday, the upper-level low
associated with the trough will further deepen as it moves into
eastern Montana, which will shift the surface flow more northerly.
As abundant moisture wraps into this system, upslope precipitation
will develop and become steadier and more widespread, especially
during the afternoon hours. There are still some differences in
the models regarding where the heaviest precipitation will be
located, however confidence is increasing that the best precip
chances will be for areas along and east of I-15 as well as areas
along the Rocky Mountain Front. Cooler, Canadian air will also
keep snow levels lower on Sunday with snow levels between 7000 and
8000 feet. Over southwest Montana, precipitation will be
widespread but off and on through the period. The system will move
further east on Monday with drier air pushing in west to east.
High temperatures will remain below average through Sunday, then
rise to near seasonal averages on Monday. MLV
Monday Night through Saturday...Extended forecast period begins with
mostly quiet conditions as the upper level system that will cross
Montana this weekend will be moving into the Upper Midwest states
and a well-amplified high pressure ridge begins to settle in over
ern Montana and the Dakotas. Meanwhile, a second upper level trof
is forecast to swing through western Canada and form a closed low
pressure center over the PACNW coast by Tues eve. With the large
ridge remaining anchored thru the middle of the country, the Pacific
low essentially becomes stationary, drifting along the coast and
occasionally moving inland during the latter half of next week.
Minor shortwaves and accompanying moisture rotating around the
central low will bring intermittent periods of showers and isolated
thunderstorms each day from Wed onward. Forecast models are in
decent agreement that most parts of central/southwest MT will see
rain during this time, but precip amounts still look to be generally
light (0.10-0.15 inch or less) over the plains and valleys.
Rainfall totals are slightly higher (0.20-0.50 inch) over the
melting snowfields of the Rocky Mtn Front and Little Belt Mtns,
which gives concern for increased streamflows in creeks/rivers in
those areas. Persistent southerly flow aloft will allow
temperatures to stay close to typical seasonal values with highs in
the mid-60s to the low 70s each day, though that will be modified
quite a bit by a fair amount of cloud cover and the timing of the
shortwave passages.
Waranauskas
&&
.AVIATION...
UPDATED 00Z.
Unsettled weather continues for the next 24 hours as rain showers
are expected to remain in the area for the entire TAF period. An
isolated thunderstorm will be possible until sunset...however not
expecting any long duration impacts so no VCTS or TSRA in the
TAFs. Ceilings and visibilities should remain VFR but brief
MVFR/IFR conditions are possible near any precipitation areas. Suk
&&
.HYDROLOGY...
Two upper level trofs, one moving through our region this weekend
and the other becoming stationary over the PACNW coast for much of
next week, will bring increased chances for rainfall over the next
several days. Though cooler temperatures will reduce snowmelt
slightly, the primary concern is that rain on the melting snowpack
will cause enhanced rises in stream/river levels. Most area rivers
are currently well below flood stage but a handful of sites are near
or approaching bankfull, so rainfall totals and river stage
forecasts will be closely monitored for significant changes and
impacts. Waranauskas
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 44 61 44 66 / 60 70 60 40
CTB 42 62 42 67 / 60 50 40 30
HLN 44 62 45 68 / 60 50 50 30
BZN 41 60 41 66 / 80 60 50 30
WEY 36 53 35 59 / 70 60 50 40
DLN 38 59 40 66 / 60 50 40 20
HVR 47 68 46 71 / 80 80 70 70
LWT 44 57 43 62 / 80 80 70 60
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
weather.gov/greatfalls
000
FXUS65 KBYZ 182129
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
329 PM MDT SAT MAY 18 2013
.SHORT TERM...VALID FOR SUN AND MON...
DEEP UPPER TROUGH OF LOW PRESSURE HAS BROUGHT SOME MUCH NEEDED
PRECIPITATION TO THE ENTIRE FORECAST AREA. THE TROUGH WILL MOVE
SLOWLY ACROSS THE AREA AND THE COOL AND WET TREND WILL CONTINUE
TONIGHT THROUGH MONDAY.
TONIGHT...SHOWERS AND THUNDERSTORMS WILL CONTINUE OVER MOST OF
THE AREA TONIGHT AS A JET SPEED MAX AND STRONG VORTICITY MOVES
ACROSS THE AREA. RAINFALL HAS BEEN HEAVY AT TIMES TODAY AND THIS
TREND WILL CONTINUE OVERNIGHT. A FEW STRONG THUNDERSTORMS MAY BE
POSSIBLE OVER EXTREME SOUTHEAST MONTANA THIS EVENING AS SURFACE
BASED CAPES PROGGED AROUND 1200 J/KG AND LI`S NEAR -4C. SURFACE
TROUGH OVER THIS AREA WILL PROVIDE GOOD SURFACE CONVERGENCE ALONG
WITH INCREASING SHEAR ALOFT. THESE FACTORS WILL AID IN THE
DEVELOPMENT OF A FEW STRONG THUNDERSTORMS OVER SOUTHERN CARTER
COUNTY THIS EVENING. THE MAIN THREAT FROM STORMS THIS EVENING WILL
BE HEAVY RAINS AS PW`S ARE AROUND 1 INCH. UPPER FORCING WILL
DIMINISH BY LATE EVENING BUT HAVE STILL CONTINUED LIKELY POPS
ACROSS THE ENTIRE AREA. FOG WILL ALSO BE POSSIBLE AFTER 06Z
TONIGHT AS LOW LEVELS WILL BE SATURATED ALONG WITH LIGHT WINDS.
SUNDAY THROUGH MONDAY...SOME DISCREPANCIES STILL EXIST WITH THE
MODELS PLACEMENT OF A DEVELOPING CLOSED UPPER LOW SUNDAY. THE
POSITIONING OF THIS LOW WILL DETERMINE HOW MUCH ADDITIONAL QPF WE
WILL RECEIVE. THE UPPER LOW WILL WRAP ENERGY BACK INTO OUR AREA
DURING THIS TIME PERIOD SO WILL CONTINUE HIGH POPS FOR NOW WITH
SOME UNCERTAINTY OF WHERE THE HEAVIEST RAINFALL WILL SETUP. THE
BEST CHANCE FOR SIGNIFICANT PRECIPITATION LOOKS TO BE OVER OUR
EASTERN ZONES WITH STRONG UPSLOPE FLOW BRINGING DECENT RAINFALL TO
OUR UPSLOPE AREAS ALONG THE FOOTHILLS AS WELL AS THE NORTHEAST BIG
HORN MOUNTAINS. WE COULD SEE AN ADDITIONA 1 TO 2 INCHES OF
PRECIPITATION ACROSS THE ENTIRE FORECAST AREA BEFORE THIS STORM
SYSTEM MOVES OUT OF THE AREA MONDAY NIGHT. LOOK FOR TEMPERATURES
TO RUN 10 TO 20 DEGREES BELOW SEASONAL NORMALS SUNDAY AND MONDAY.
RICHMOND
.LONG TERM...VALID FOR TUE...WED...THU...FRI...SAT...
MINIMAL CHANGES FOR THE EXTENDED PERIOD AT THIS TIME...AS SOME
DISCREPANCY IN MODELS REMAIN THROUGH PERIOD AS TO DETAILS.
HOWEVER THE OVERALL PATTERN REMAIN PRETTY COMPARABLE. TEMPERATURES
THROUGH THE PERIOD WILL BE ON THE RISE...WITH AROUND NORMAL
TEMPERATURES EXPECTED FOR TUESDAY AND WEDNESDAY...AND A FEW
DEGREES ABOVE NORMAL THEREAFTER.
SOME DEGREE OF RIDGING IS PROGGED TO DEVELOP ACROSS THE
REGION...BETWEEN SYSTEMS...BEGINNING TUESDAY. THE CURRENT
WEATHER SYSTEM ACTS AS A BLOCKING FEATURE IN THE EAST HOLDING UP
THE PROGRESSION OF THE NEXT SYSTEM. SOUTHWEST FLOW AHEAD OF THE
THE LOW CENTERED OVER NORTHWESTERN WASHINGTON BY WEDNESDAY
NIGHT...AND SENDS A SIGNIFICANT SHORTWAVE ACROSS THE REGION
OVERNIGHT. GFS IS MUCH DRIER THAN THE EC WITH THIS SYSTEM...BUT
CAN SEE SOME POTENTIAL WITH HEATING...SHORTWAVE...AND POSSIBLE TAP
INTO GULF MOISTURE SETTING UP. SOUTHWEST FLOW REMAINS IN
PLACE...BUT APPEARS TO TAP IN TO DRY AIR ALOFT FOLLOWING THIS
WAVE...HOWEVER THERE CONTINUES TO BE SOME INDICATION OF A GULF
MOISTURE TAP AT THE SURFACE THROUGH THE REMAINDER OF THE EXTENDED
PERIOD. SFC MOISTURE FROM RECENT RAINS AND POSSIBLE GULF MOISTURE
INFLUX...COMBINED WITH DAYTIME HEATING AND LIKELY WEAK SHORTWAVES
RADIATING THROUGH THE FLOW SHOULD ALLOW FOR AT LEAST ISOLATED
THUNDER POTENTIAL IN THE AFTERNOON...AND POSSIBLE REMNANT SHOWERS
INTO THE OVERNIGHT HOURS. KEPT INHERITED POPS IN PLACE...BUT
SPREAD SLIGHT POPS ACROSS THE PLAINS THROUGH THE LATTER HALF OF
THE EXTENDED PERIOD. AAG
&&
.AVIATION...
SHOWERS AND THUNDERSTORMS CONTINUE TO BECOME INCREASINGLY
WIDESPREAD...IMPACTING MUCH OF THE REGION WEST OF KMLS. SHOWERS
AND THUNDERSTORMS ARE EXPECTED TO SHIFT FURTHER EAST AND
NORTHEAST THROUGHOUT EVENING...AND PERSIST OVERNIGHT AND THROUGH
SUNDAY. SOME OF THE STORMS WILL CONTAIN MODERATE TO BRIEFLY HEAVY
RAINFALL AND COULD LOWER CONDITIONS TO MVFR/IFR. MOUNTAINS WILL BE
OBSCURED IN SHOWERS AND CLOUDS THROUGHOUT THE DAY. AAG
&&
.PRELIMINARY POINT TEMP/POPS...
SUN MON TUE WED THU FRI SAT
-----------------------------------------------------------
BIL 048/058 048/062 044/071 047/072 049/073 049/076 050/076
88/T 86/W 31/B 12/T 42/T 22/T 22/T
LVM 041/057 040/059 037/067 041/072 040/069 041/071 042/071
87/T 85/W 31/B 14/T 43/T 33/T 33/T
HDN 048/062 047/062 045/071 045/074 049/076 048/078 049/078
98/T 86/W 31/E 12/T 32/T 22/T 22/T
MLS 051/063 049/062 046/068 046/072 050/073 048/075 051/076
+8/T 86/W 53/W 22/T 22/T 22/T 22/T
4BQ 048/059 047/060 044/065 044/072 048/073 047/075 050/076
+8/T 87/W 53/W 11/B 22/T 22/T 22/T
BHK 048/060 047/060 043/062 043/068 048/069 048/073 050/076
+8/T 87/W 63/W 21/B 22/T 22/T 22/T
SHR 047/056 043/057 041/065 040/074 046/074 045/076 047/076
77/T 87/W 42/W 12/T 32/T 22/T 22/T
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
000
FXUS65 KGGW 182102
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
302 PM MDT SAT MAY 18 2013
.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH MONDAY...
A LARGE TROUGH HAS DUG IN OVER THE SOUTH WEST CONUS WITH A RIDGE
OVER WESTERN CANADA. VARIABLE IMPULSES OF ENERGY MOVING UP FROM
THE DOWNSTREAM PART OF THE SOUTHERN TROUGH WILL SUPPORT CONTINUED
PRECIPITATION THROUGH MONDAY AFTERNOON. RAINFALL IS ALSO SUPPORTED
BY A SURFACE LOW SOUTHEAST OF MONTANA THAT IS DRAWING LOW LEVEL
MOISTURE INTO THE AREA.
SYSTEM CONTINUES TO STRENGTHEN AND GRADUALLY MOVE EASTWARD...WITH
THE EFFECTS EXITING NORTHEAST MONTANA MONDAY NIGHT. ON
MONDAY...MOST OF THE MODELS HAVE MOST OF THE PRECIPITATION TO THE
SOUTHEAST PART OF THE CWA...BUT WITH POTENTIALLY HIGHER AMOUNTS
THAN EARLIER IN THE FORECAST. SOUNDINGS ARE VERY SATURATED WITH
AROUND AN INCH OF PRECIPITABLE WATER..LEADING TO THE FORECAST OF
MOSTLY RAIN SHOWERS. SOME INSTABILITY IN THE SOUNDINGS WILL LEAD
TO SOME LIMITED THUNDERSTORM ACTIVITY. THUNDERSTORMS ARE LIMITED
BY THE LACK OF CAP...WHICH WILL NOT ALLOW MUCH BUILD-UP OF
CONVECTIVE ENERGY. WINDS WILL PICK A LITTLE FROM THE NORTH ON
SUNDAY AS THE SURFACE LOW TIGHTENS...HOWEVER...THEY SHOULD STAY
BELOW 20KTS...WITH LOCALLY HIGHER GUSTS POSSIBLE IN OUTFLOW AREAS. MARTIN
.LONG TERM...MONDAY NIGHT THROUGH SATURDAY...
THE ONLY CHANGES IN THE SHORT TERM LOOK TO BE STRONGER WINDS
THURSDAY AND THE POSSIBILITY FOR A SEVERE EVENT OR TWO AT THE END
OF THE PERIOD.
THE GFS WANTS TO RAMP UP WINDS QUITE A BIT THURSDAY AFTERNOON WITH
850 WINDS OVER THE CWA APPROACHING 50 KNOTS AS A MID LEVEL HIGH
OVER THE MINNESOTA AND ONTARIO REGION BATTLES WITH THE APPROACHING
PACIFIC NORTHWEST LOW. THE ECMWF HAS A BIT LESS AMPLIFIED GRADIENT
AND THUS A THINNER BAND OF STRONG 850 WINDS OVER THE CWA...BUT HAS
A SIMILAR UPPER PATTERN AS GFS. WENT CLOSER TO THE ECMWF SOLUTION
AS THE GFS TENDS TO HAVE WINDS A BIT HIGH OVER THE AREA.
AS THE UPPER LOW APPROACHES FOR THE WEEKEND...LOBES OF SHORTWAVE
ENERGY MAY CONTINUE TO BRING CHANCES FOR THUNDERSTORM DEVELOPMENT.
SATURDAY AFTERNOON HAS THE GFS AND ECMWF PUTTING OUT OVER 2000
J/KG OF CAPE OVER PARTS OF THE AREA...SO THERE WILL BE PLENTY OF
INSTABILITY OVER THE REGION. SUNDAY AFTERNOON AND EVENING SHOWS ROUGHLY
THE SAME SCENARIO...AND EVEN DIPS INTO MONDAY AS THE LOW SLOWLY
PROGRESSES NORTHWARD OFF TO OUR WEST AND NORTHWEST. THIS WILL
PROVIDE BROAD SOUTHWEST FLOW ALOFT FOR THE WEEKEND...WHICH SHOULD
GIVE ENOUGH UPPER LEVEL SUPPORT WITH DIFLUENT FLOW COMBINED WITH
LOBES OF SHORTWAVE ENERGY OFF THE MAIN FLOW...ESPECIALLY FOR
SATURDAY. FOR NOW...THE GFS HAS A WARM FRONT PASS THROUGH THE CWA
FRIDAY...AND THE ECMWF HAS ONE PASS SATURDAY. MORE MODEL AGREEMENT
ON TIMING WILL SHOW IF WE GET OUR FIRST SIGNIFICANT ROUND OF
STORMS THIS SEASON NEXT WEEKEND. BARNWELL
PREVIOUS LONG TERM DISCUSSION...THE EXTENDED FORECAST BEGINS
MONDAY NIGHT WITH AN UPPER LOW EXITING INTO THE UPPER MISSISSIPPI
RIVER VALLEY AND WEAK RIDGING BUILDING INTO NORTHEASTERN MONTANA.
BY WEDNESDAY MORNING ANOTHER UPPER LOW MOVES IN OVER THE PACIFIC
NORTHWEST SETTING UP DI-FLUENT SOUTHWEST FLOW ALOFT OVER THE AREA
THROUGH THE END OF THE EXTENDED.
THIS WILL CONTINUE THE COOLISH TEMPERATURES DURING THE DAY AND
NEAR NORMAL TEMPERATURES AT NIGHT. PRECIPITATION CHANCES SHOULD
RANGE SLIGHTLY ABOVE NORMAL... HOWEVER PIN POINTING ANY BETTER
DAYS THAN OTHERS WILL BE VERY HARD.
ENSEMBLES OF THE GFS AND EC SHOW HIGH CONFIDENCE IN AN UPPER LOW
OVER THE PACIFIC NORTHWEST...HOWEVER DO HAVE TROUBLE KEEPING THE
DAY TO DAY PLACEMENT OF THE UPPER LOW THE SAME. RMOP IS PRETTY
GOOD FOR UPPER LOWS OVER THE PACIFIC NORTHWEST. MODERATE TO HIGH
CONFIDENCE ON THE PATTERN. HOWEVER THE PATTERN IS MORE SHOWERY IN
NATURE NOT ALLOWING FOR THE CONFIDENCE TO DOUBLE OF CLIMO POPS AT
THIS TIME. PROTON
&&
.AVIATION...
A MIX OF VFR WITH PERIODS OF MVFR CAN BE EXPECTED THROUGH THE
PERIOD AT ALL TERMINALS. SOUTHWEST FLOW ALOFT AND MOIST EAST TO
SOUTHEAST FLOW WILL KEEP SKIES BROKEN TO OVERCAST. CEILINGS WILL
BE TRICKY... GUIDANCE HAS A SPLIT WITH ONE GOING FOR SOLID
MVFR...THE OTHER SOLID VFR. WILL GO WITH THE PREDOMINATE OF VFR
AND PERIODS OF MVFR MAINLY FOR MORNING LOWER CEILINGS AND ANY
AFTERNOON CBS THAT FORM. LIGHT RAIN SHOWERS ARE EXPECTED ON AND
OFF THROUGHOUT THE ENTIRE TAF PERIOD.
KOLF ASOS IS NOT TRANSMITTING THE OBSERVATIONS FOR US TO SEE THEM
ONLINE AND INSTEAD WE ARE HAVING TO CALL EVERY HOUR. THEREFORE THE
TAF IS AMD NOT SKED.
PROTON/FRANSEN
&&
.HYDROLOGY...
THE NEXT FEW DAYS WILL BE RATHER WET AS AN UPPER-LEVEL TROUGH
AFFECTS THE AREA. SEVERAL DISTURBANCES ASSOCIATED WITH THIS TROUGH
WILL PASS THROUGH WHICH WILL KEEP CHANCES FOR RAIN WITH SOME
THUNDERSTORMS THROUGH EARLY NEXT WEEK. MODEL GUIDANCE DEPICTS HIGH
AMOUNTS OF MOISTURE WITH THIS SYSTEM. AT THIS POINT THE
ENVIRONMENT LOOKS FAVORABLE FOR SLOW-MOVING STORMS WITH HIGHER
PRECIPITATION IN LOCALIZED AREAS.
MOST OF THE BASINS IN NORTHEAST MONTANA WILL BE ABLE TO ACCOMMODATE
THIS AMOUNT OF MOISTURE... AT LEAST EARLY ON IN THE EVENT. THERE IS
SOME CONCERN FOR RAPIDLY RISING STREAMS...FIELD FLOODING AND
LOCALIZED FLOODING IN TOWNS AS THE EVENT PERSISTS. SOME MINOR
FLOODING MAY BECOME AN ISSUE... ESPECIALLY FOR THE AREAS FROM
GLASGOW TO CIRLE AND EASTWARD INTO NORTH DAKOTA WHERE THE POTENTIAL
FOR STRONGER THUNDERSTORMS IS HIGHER.
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
WEATHER.GOV/GLASGOW
000
FXUS65 KTFX 182057
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
257 PM MDT Sat May 18 2013
.DISCUSSION...
Tonight through Monday...Scattered showers and isolated
thunderstorms are developing this afternoon as instability
increases with an upper-level trough pushing through the Northern
Rockies. With the cooler air aloft, some of these showers and
thunderstorms may contain graupel. On Sunday, the upper-level low
associated with the trough will further deepen as it moves into
eastern Montana, which will shift the surface flow more northerly.
As abundant moisture wraps into this system, upslope precipitation
will develop and become steadier and more widespread, especially
during the afternoon hours. There are still some differences in
the models regarding where the heaviest precipitation will be
located, however confidence is increasing that the best precip
chances will be for areas along and east of I-15 as well as areas
along the Rocky Mountain Front. Cooler, Canadian air will also
keep snow levels lower on Sunday with snow levels between 7000 and
8000 feet. Over southwest Montana, precipitation will be
widespread but off and on through the period. The system will move
further east on Monday with drier air pushing in west to east.
High temperatures will remain below average through Sunday, then
rise to near seasonal averages on Monday. MLV
Monday Night through Saturday...Extended forecast period begins with
mostly quiet conditions as the upper level system that will cross
Montana this weekend will be moving into the Upper Midwest states
and a well-amplified high pressure ridge begins to settle in over
ern Montana and the Dakotas. Meanwhile, a second upper level trof
is forecast to swing through western Canada and form a closed low
pressure center over the PACNW coast by Tues eve. With the large
ridge remaining anchored thru the middle of the country, the Pacific
low essentially becomes stationary, drifting along the coast and
occasionally moving inland during the latter half of next week.
Minor shortwaves and accompanying moisture rotating around the
central low will bring intermittent periods of showers and isolated
thunderstorms each day from Wed onward. Forecast models are in
decent agreement that most parts of central/southwest MT will see
rain during this time, but precip amounts still look to be generally
light (0.10-0.15 inch or less) over the plains and valleys.
Rainfall totals are slightly higher (0.20-0.50 inch) over the
melting snowfields of the Rocky Mtn Front and Little Belt Mtns,
which gives concern for increased streamflows in creeks/rivers in
those areas. Persistent southerly flow aloft will allow
temperatures to stay close to typical seasonal values with highs in
the mid-60s to the low 70s each day, though that will be modified
quite a bit by a fair amount of cloud cover and the timing of the
shortwave passages.
Waranauskas
&&
.AVIATION...
UPDATED 1748Z.
An upper level trough extending from the Great Basin area into the
Northern Rockies will make only slow eastward progress today...
keeping central and southwest MT under BKN-OVC skies. Light
rainshowers will gradually redevelop across the area this
afternoon...starting first in the vicinity of higher terrain then
becoming widespread. There is also a slight chance for isolated
thunderstorms this aftn, but given their low probability and spotty
coverage did not include mention of any TS at primary TAF sites
today. Ceilings and visibilities should remain VFR but brief
MVFR/IFR conditions are possible near any precipitation areas.
Shower activity will diminish after 19/06Z. Another wave generates
light rain for the north central plains from east to west early
Sunday. Winds will remain light at all stations. Nutter/MLV
&&
.HYDROLOGY...
Two upper level trofs, one moving through our region this weekend
and the other becoming stationary over the PACNW coast for much of
next week, will bring increased chances for rainfall over the next
several days. Though cooler temperatures will reduce snowmelt
slightly, the primary concern is that rain on the melting snowpack
will cause enhanced rises in stream/river levels. Most area rivers
are currently well below flood stage but a handful of sites are near
or approaching bankfull, so rainfall totals and river stage
forecasts will be closely monitored for significant changes and
impacts. Waranauskas
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 44 61 44 66 / 60 70 60 40
CTB 42 62 42 67 / 60 50 40 30
HLN 44 62 45 68 / 60 50 50 30
BZN 41 60 41 66 / 80 60 50 30
WEY 36 53 35 59 / 70 60 50 40
DLN 38 59 40 66 / 60 50 40 20
HVR 47 68 46 71 / 80 80 70 70
LWT 44 57 43 62 / 80 80 70 60
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
weather.gov/greatfalls
000
FXUS65 KMSO 182040
AFDMSO
Area Forecast Discussion
National Weather Service Missoula MT
240 PM MDT Sat May 18 2013
.DISCUSSION...Low level moisture from rain the last 24 hours
combined with an unstable atmosphere and surface heating is
producing numerous showers across much of the Northern Rockies
this afternoon. An isolated lightning strike or two are possible
with any shower this afternoon. Expect showers to persist through
the early evening hours with the exception of the continental
divide where showers will continue through Sunday morning. This
same scenario is expected Sunday.
Monday and Tuesday a weak ridge will nose its way into the region.
Sufficient low level moisture and heating will provide the
potential for showers in the afternoon again but be limited to
southwest Montana and along the divide.
Much warmer temperatures Monday and Tuesday will return with
highs in the mid to upper 70s. Enjoy the warm and relatively dry
weather Monday and Tuesday as the pattern will change by mid
week.
Few changes to the forecast for Wednesday and beyond. Confidence
remains high for a closed low to impact the northern Rockies
Wednesday afternoon or evening bringing scattered. A few may contain
heavy rain.
Thursday through Memorial weekend is expected to be much cooler
and wet. The closed low will move over the northern Rockies and
remain nearly stationary. Confidence is high for rain during this
time frame. Some areas could receive significant amounts but
confidence on the timing and location of heavier amounts are
uncertain at this time.
Small stream flooding in northwest Montana remains a potential
concern with heavy rain, however, the slower timing of the system
raises the potential for overnight snow. In this scenario, travel
over mountain passes would be difficult and heavy snow at times
would cause slush on the roads even at lower elevations.
&&
.AVIATION...Showers will continue to develop and increase in
coverage as the evening hours neat, then decrease in coverage after
sunset. There is a slight chance for thunderstorm development
later this afternoon that could impact all aviation sites. These
storms will likely be week and short lived. Visibility and
ceilings will drop with the showers and thunderstorms, as well as
obstructing mountain terrain. Showers will again linger around
western Montana and central Idaho for Sunday.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&
$$
Follow us on Facebook and Twitter!
https://www.facebook.com/US.NationalWeatherService.Missoula.gov
https://www.twitter.com/NWSMissoula
000
FXUS65 KTFX 181748
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1148 AM MDT Sat May 18 2013
Aviation Section Updated
.UPDATE...
Very few updates this morning as current forecast is on track.
There will be breaks in the showers today with better coverage of
showers and isolated thunderstorms this afternoon, but overcast
skies will keep temperatures slightly cooler than seasonal
averages. MLV
&&
.AVIATION...
UPDATED 1748Z.
An upper level trough extending from the Great Basin area into the
Northern Rockies will make only slow eastward progress today...
keeping central and southwest MT under BKN-OVC skies. Light
rainshowers will gradually redevelop across the area this
afternoon...starting first in the vicinity of higher terrain then
becoming widespread. There is also a slight chance for isolated
thunderstorms this aftn, but given their low probability and spotty
coverage did not include mention of any TS at primary TAF sites
today. Ceilings and visibilities should remain VFR but brief
MVFR/IFR conditions are possible near any precipitation areas.
Shower activity will diminish after 19/06Z. Another wave generates
light rain for the north central plains from east to west early
Sunday. Winds will remain light at all stations. Nutter/MLV
&&
.HYDROLOGY...
Two upper level trofs, one moving through our region this weekend
and the other becoming stationary over the PACNW coast for much of
next week, will bring increased chances for rainfall over the next
several days. Though cooler temperatures will reduce snowmelt
slightly, the primary concern is that rain on the melting snowpack
will cause enhanced rises in stream/river levels. Most area rivers
are currently well below flood stage but a handful of sites are near
or approaching bankfull, so rainfall totals and river stage
forecasts will be closely monitored for significant changes and
impacts. Waranauskas
&&
.PREV DISCUSSION...
/ISSUED 525 AM MDT Sat May 18 2013/
Upper level trough extending from the Pacific NW through the Great
Basin will continue a slow progression east into the Rocky Mtn
region today, keeping the forecast area under a moist and somewhat
unstable SW flow aloft. Main focus for precipitation this morning
will be along an old/weakening deformation zone along the Hi-line
and over far SW MT ahead of the next incoming shortwave embedded
within the broader upper trough. Elsewhere, precipitation will be
limited to scattered light showers with patchy fog/drizzle through
early this morning. Daytime heating and the approaching shortwave
from the south should bring an increase in the coverage of showers
this afternoon and evening to most of the forecast area and an
isolated weak/brief thunderstorm or two cannot be ruled out,
however instability parameters are rather marginal. Sunday and
Monday, the upper trough emerges east of the Rockies with the
upper level circulation closing off as the trough undercuts an
upper ridge over central Canada. This results in a shift to more
northerly flow across the forecast area as the upper low center
tracks from Nebraska slowly northeast into the upper Midwest
through early next week. This should shift the focus for
widespread precipitation to north central MT, however all areas
will have some chance for showers through the period, especially
during the afternoon/evening time-frames. Temperatures will remain
close to seasonal averages today with slightly cooler conditions
on Sunday as the flow aloft turns to the north. Snow levels at or
above 8000 ft will limit any snow accumulation to the higher
peaks. Hoenisch
Monday Night through Saturday...Extended forecast period begins with
mostly quiet conditions as the upper level system that will cross
Montana this weekend will be moving into the Upper Midwest states
and a well-amplified high pressure ridge begins to settle in over
ern Montana and the Dakotas. Meanwhile, a second upper level trof
is forecast to swing through western Canada and form a closed low
pressure center over the PACNW coast by Tues eve. With the large
ridge remaining anchored thru the middle of the country, the Pacific
low essentially becomes stationary, drifting along the coast and
occasionally moving inland during the latter half of next week.
Minor shortwaves and accompanying moisture rotating around the
central low will bring intermittent periods of showers and isolated
thunderstorms each day from Wed onward. Forecast models are in
decent agreement that most parts of central/southwest MT will see
rain during this time, but precip amounts still look to be generally
light (0.10-0.15 inch or less) over the plains and valleys.
Rainfall totals are slightly higher (0.20-0.50 inch) over the
melting snowfields of the Rocky Mtn Front and Little Belt Mtns,
which gives concern for increased streamflows in creeks/rivers in
those areas. Persistent southerly flow aloft will allow
temperatures to stay close to typical seasonal values with highs in
the mid-60s to the low 70s each day, though that will be modified
quite a bit by a fair amount of cloud cover and the timing of the
shortwave passages.
Waranauskas
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 64 45 59 45 / 80 60 80 80
CTB 62 44 60 43 / 80 50 80 80
HLN 64 45 60 45 / 70 60 60 70
BZN 64 43 59 42 / 80 70 60 60
WEY 55 36 53 34 / 80 70 60 40
DLN 61 40 58 40 / 80 60 50 50
HVR 69 49 66 47 / 90 80 90 80
LWT 61 45 57 43 / 80 80 80 80
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
weather.gov/greatfalls
000
FXUS65 KGGW 181540
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
940 AM MDT SAT MAY 18 2013
.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH MONDAY...
UPDATED FORECAST TO ACCOUNT FOR RADAR PPT TRENDS AND SHORT TERM
MODEL FORECASTS. MORNING SOUNDING IS SATURATED WITH PRECIPITABLE
WATER OF ABOUT AN INCH...WHICH IS CLOSE TO THE 99TH PERCENTILE FOR
THIS TIME OF YEAR. DEEP WET AND UNCAPPED SOUNDING IS
CHARACTERISTIC OF A PERSISTENT RAIN EVENT...WITH SOME THUNDER
POSSIBLE. HOWEVER...HAVE DEEMPHASIZED THE IMPACT FROM
THUNDERSTORMS AS RAIN IS THE MAIN IMPACT. DISORGANIZED UPPER FLOW
WITH WEAK TO MODEST DYNAMIC FORCING SUGGESTS PERIODS OF RAIN OFF
AND ON FOR THE NEXT 2 OR 3 DAYS WITH SPECIFIC LOCATIONS RECEIVING
THE MOST RAIN DIFFICULT TO PIN DOWN. MODELS DO DIFFER ON WHEN RAIN
WILL TAPER OFF WITH THE GFS MODEL MORE RAPIDLY PROGRESSING THE
SYSTEM EASTWARD...HOWEVER...TEND TO FAVOR THE EC AND NAM MODELS
WHICH HAVE HAD GREATER RUN TO RUN CONSISTENCY. MARTIN
PREVIOUS DISCUSSION...
TODAY THROUGH MONDAY...MAIN CONCERN WILL BE THE CONTINUATION OF
WET WEATHER ACROSS NORTHEAST MONTANA. CURRENT RADAR OBSERVATIONS
EARLY THIS MORNING ARE SHOWING A RATHER EXPANSIVE AREA OF SHOWER
ACTIVITY ACROSS THE CWA. SOME 40-50 DBZ REFLECTIVITY HAS BEEN
OCCURRING FROM TIME TO TIME IN VERY ISOLATED LOCATIONS AND SO
CANNOT RULE OUT A RUMBLE OF THUNDER THIS MORNING.
MODELS ARE IN EXCELLENT AGREEMENT WITH THE OVERALL SYNOPTIC
PATTERN KEEPING IN AN UPPER LEVEL TROUGH PERSISTING ACROSS THE CWA
WHICH WILL PROVIDE A CONTINUATION OF UNSETTLED WEATHER CONDITIONS.
HOWEVER...THERE ARE NOTABLE DIFFERENCES FROM THE MODELS IN THE DETAILS
AND HANDLING OF MESOSCALE CONVECTION THAT DEVELOPS. THE GFS IN
PARTICULAR HAS NOT BEEN PERFORMING WELL IN THE PLACEMENT OF QPF
WITH RECENT RAIN SHOWER ACTIVITY AND THEREFORE HAVE DISCOUNTED IT
FOR THE SHORT TERM FORECAST PERIOD. THE 00Z ECMWF AND THE LATEST
HRRR HAVE SHOWN TO HAVE A PRETTY GOOD HANDLE ON THE OVERALL
SITUATION AND LEANED WITH A COMPROMISE OF THEIR SOLUTIONS IN LARGE
PART FOR THE FORECAST. IN A NUTSHELL...UPPER LEVEL SHORTWAVE
FEATURES WILL PROPAGATE THROUGH SOUTHWEST FLOW ALOFT WHICH ALONG
WITH UPPER LEVEL DIFFLUENCE WILL HELP FORCE VERTICAL ASCENT. A
SURFACE LOW PRESSURE WILL ALSO SIT AND SPIN ACROSS THE DAKOTAS
THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK WHICH WILL CONTINUE
TO PROVIDE MOIST EASTERLY FLOW INTO NORTHEAST MONTANA. GIVEN THESE
CIRCUMSTANCES...FEEL VERY CONFIDENT IN WIDESPREAD MEASURABLE
RAINFALL ACCUMULATIONS.
THE CHALLENGE WITH THIS FORECAST WILL BE DETERMINING WHERE THE
HEAVIEST AMOUNTS OF RAINFALL WILL OCCUR...WHICH WILL LARGELY
DEPEND UPON MESOSCALE DETAILS THAT ARE DIFFICULT TO PINPOINT WITH
MUCH CONFIDENCE AT THIS TIME. AREAS WITH HEAVIEST RAINFALL MAY
CERTAINLY PICK UP OVER AN INCH OF RAINFALL...IF NOT MORE...THROUGH
EARLY NEXT WEEK. GIVEN THESE ARGUMENTS...WILL GO WITH CATEGORICAL
POPS IN MOST PLACES THROUGH SUNDAY NIGHT AND TAPER TO LIKELY POPS
ON MONDAY AS THE UPPER TROUGH BEGINS TO TRANSLATE EASTWARD AND THE
SURFACE LOW EXITS THE DAKOTAS AND HEADS FOR SW MN AND NW IA. NAM
BUFR SOUNDINGS CONTINUE TO INDICATE LI READINGS AROUND 0 OR
SLIGHTLY NEGATIVE ACROSS PARTS OF THE CWA AT TIMES GOING INTO
TONIGHT...AND INDICATE SMALL AMOUNTS OF CAPE AND SOME INSTABILITY.
DECIDED TO KEEP A SLIGHT MENTION FOR THUNDER IN THE GRIDS GIVEN
THESE ARGUMENTS. NO LARGE SWINGS IN TEMPERATURES ARE EXPECTED
THROUGH THE SHORT TERM SINCE THE OVERALL PATTERN WILL REMAIN
RATHER STATIC. THEREFORE WILL EXPECT SEASONAL HIGHS AND LOWS
THROUGH EARLY NEXT WEEK. MALIAWCO
.LONG TERM...MONDAY NIGHT THROUGH SATURDAY...
THE EXTENDED FORECAST BEGINS MONDAY NIGHT WITH AN UPPER LOW
EXITING INTO THE UPPER MISSISSIPPI RIVER VALLEY AND WEAK RIDGING
BUILDING INTO NORTHEASTERN MONTANA.
BY WEDNESDAY MORNING ANOTHER UPPER LOW MOVES IN OVER THE PACIFIC
NORTHWEST SETTING UP DI-FLUENT SOUTHWEST FLOW ALOFT OVER THE AREA
THROUGH THE END OF THE EXTENDED.
THIS WILL CONTINUE THE COOLISH TEMPERATURES DURING THE DAY AND
NEAR NORMAL TEMPERATURES AT NIGHT. PRECIPITATION CHANCES SHOULD
RANGE SLIGHTLY ABOVE NORMAL... HOWEVER PIN POINTING ANY BETTER
DAYS THAN OTHERS WILL BE VERY HARD.
ENSEMBLES OF THE GFS AND EC SHOW HIGH CONFIDENCE IN AN UPPER LOW
OVER THE PACIFIC NORTHWEST...HOWEVER DO HAVE TROUBLE KEEPING THE
DAY TO DAY PLACEMENT OF THE UPPER LOW THE SAME. RMOP IS PRETTY
GOOD FOR UPPER LOWS OVER THE PACIFIC NORTHWEST. MODERATE TO HIGH
CONFIDENCE ON THE PATTERN. HOWEVER THE PATTERN IS MORE SHOWERY IN
NATURE NOT ALLOWING FOR THE CONFIDENCE TO DOUBLE OF CLIMO POPS AT
THIS TIME. PROTON
&&
.AVIATION...
A MIX OF VFR WITH PERIODS OF MVFR CAN BE EXPECTED THROUGH THE
PERIOD AT ALL TERMINALS. SOUTHWEST FLOW ALOFT AND MOIST EAST TO
SOUTHEAST FLOW WILL KEEP SKIES BROKEN TO OVERCAST. CEILINGS WILL
BE TRICKY... GUIDANCE HAS A SPLIT WITH ONE GOING FOR SOLID
MVFR...THE OTHER SOLID VFR. WILL GO WITH THE PREDOMINATE OF VFR
AND PERIODS OF MVFR MAINLY FOR MORNING LOWER CEILINGS AND ANY
AFTERNOON CBS THAT FORM. LIGHT RAIN SHOWERS ARE EXPECTED ON AND
OFF THROUGHOUT THE ENTIRE TAF PERIOD.
KOLF ASOS IS NOT TRANSMITTING THE OBSERVATIONS FOR US TO SEE THEM
ONLINE AND INSTEAD WE ARE HAVING TO CALL EVERY HOUR. THEREFORE THE
TAF IS AMD NOT SKED.
PROTON/FRANSEN
&&
.HYDROLOGY...
THE NEXT FEW DAYS WILL BE RATHER WET AS AN UPPER-LEVEL TROUGH
AFFECTS THE AREA. SEVERAL DISTURBANCES ASSOCIATED WITH THIS TROUGH
WILL PASS THROUGH WHICH WILL KEEP CHANCES FOR RAIN WITH SOME
THUNDERSTORMS THROUGH EARLY NEXT WEEK. MODEL GUIDANCE DEPICTS HIGH
AMOUNTS OF MOISTURE WITH THIS SYSTEM. AT THIS POINT THE
ENVIRONMENT LOOKS FAVORABLE FOR SLOW- MOVING STORMS WITH HIGHER
PRECIPITATION IN LOCALIZED AREAS.
MOST OF THE BASINS IN NORTHEAST MONTANA WILL BE ABLE TO ACCOMMODATE
THIS AMOUNT OF MOISTURE... AT LEAST EARLY ON IN THE EVENT. THERE IS
SOME CONCERN FOR RAPIDLY RISING STREAMS AND LOCALIZED URBAN
FLOODING AS THE EVENT PERSISTS. SOME FLOODING MAY BECOME AN
ISSUE... ESPECIALLY FOR THE EASTERN AND SOUTHERN COUNTIES WHERE
THE POTENTIAL FOR STRONGER THUNDERSTORMS IS HIGHER.
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
WEATHER.GOV/GLASGOW
000
FXUS65 KBYZ 181519
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
919 AM MDT SAT MAY 18 2013
.UPDATE...
HAVE MADE SOME CHANGES TO THE MORNING FORECAST. GFS/ECMWF/NAM12
ARE IN GOOD AGREEMENT IN LIFTING ANOTHER WAVE ACROSS THE AREA THIS
MORNING. RADAR RETURNS HAVE BEEN INCREASING OVER SOUTH CENTRAL
MONTANA THIS MORNING WITH UPPER JET BRINGING A SHORT WAVE INTO THE
AREA ALONG WITH INCREASING QG FORCING. A FEW EMBEDDED
THUNDERSHOWERS ALSO POSSIBLE WITH WEAK LOW LEVEL INSTABILITY. HAVE
RAISED POPS TO LIKELY FROM BILLINGS WEST FOR THIS MORNING. LOWERED
POPS IN THE EAST FOR THIS MORNING AS FORCING FROM THE UPPER LEVEL
TROUGH WILL NOT IMPACT SOUTHEAST MONTANA UNTIL AFTER 18Z TODAY.
PATCHY FOG ACROSS THE AREA IS QUICKLY LIFTING AND WILL REMOVE IT
FROM THE FORECAST. NO CHANGES TO TEMPERATURE FORECAST THEY LINE UP
WELL WITH CURRENT GUIDANCE. RICHMOND
&&
.SHORT TERM...VALID FOR TDY AND SUN...
RAINFALL TOTALING AN INCH OR MORE STILL LOOKS LIKE A GOOD BET OVER
THE NEXT FEW DAYS IN MANY AREAS. HOWEVER...THE 500-HPA TROUGH THAT
IS SET TO DRIVE ONE OF THE BETTER PRECIPITATION EVENTS WE HAVE HAD
IN A LONG TIME IS SURPRISING COMPLEX...SO SOME UNCERTAINTY EXISTS.
TODAY...THE MID-LEVEL SHORT WAVE TROUGH CENTERED NEAR 700 HPA THAT
IS SEEN ENTERING WESTERN WY ON 09 UTC MOISTURE CHANNEL IMAGES WILL
MOVE INTO SOUTHERN MT. THE ECMWF HAS BEEN THE MOST CONSISTENT WITH
BRINGING THIS BATCH OF FORCING INTO THE AREA IN THE LAST FEW DAYS.
ITS 00 UTC RUN CONTINUES THIS THEME...GENERATING CONVECTION ACROSS
MUCH OF THE AREA AFTER 18 UTC...WITH QPF AMOUNTS OF A QUARTER TO A
HALF INCH. THE 00 UTC GFS HAS FINALLY PICKED UP ON THIS SHORT WAVE
TOO...SO OUR CONFIDENCE IN PRECIPITATION HAS INCREASED ENOUGH THAT
WE HAVE CHOSEN TO ADVERTISE 90 TO 100 PERCENT POPS AFTER 18 UTC IN
THE BILLINGS...SHERIDAN...MILES CITY...AND BROADUS AREAS. THE 700-
500 HPA LAPSE RATES ARE MODEST AROUND 6 C/KM...BUT THERE IS ENOUGH
INSTABILITY /POCKETS OF MUCAPE UP TO 500 J/KG/ TO GENERATE THUNDER
AS WELL. CALIBRATED THUNDERSTORM PROBABILITIES OFF THE 03 UTC SREF
JUMP UP INTO THE 40 AND 50 PERCENT RANGE AFTER 18 UTC AS WELL. THE
SEVERE RISK IS NEGLIGIBLE THOUGH GIVEN THE EXPECTED INSTABILITY. A
CAUTIONARY NOTE ABOUT THE POP FORECAST IS THAT MANY WRF-BASED HIGH
RESOLUTION MODELS FROM 00 UTC CLUSTER CONVECTION FURTHER SOUTHEAST
FROM SHERIDAN TOWARD BROADUS...WHICH MAY ACTUALLY SUPPRESS SOME OF
THE PRECIPITATION FURTHER NORTH IN PLACES LIKE BILLINGS. NOTE THAT
WE ALSO DECIDED TO CARRY ONLY CHANCE POPS IN MANY PLACES BEFORE 18
UTC BASED ON UPSTREAM TRENDS AND RECENT RAP AND HRRR OUTPUT.
TONIGHT...WE CONTINUED LEANING ON THE 00 UTC ECMWF SOLUTION DURING
THE EVENING...WITH A CONCENTRATED AREA OF CATEGORICAL POPS FOR THE
PLAINS OF SOUTH CENTRAL AND SOUTHEASTERN MT BEFORE 06 UTC. WE THEN
LET POPS FALL BACK A BIT AFTER MIDNIGHT IN MANY AREAS SINCE 1/ THE
DIURNALLY-DRIVEN CONVECTION SHOULD DIMINISH WITH SUNSET...AND 2/ A
BREAK IN FORCING SHOULD TAKE PLACE AS THE 700-HPA SHORT WAVE MOVES
OUT AND/OR WEAKENS. IF THE ECMWF IS CORRECT...WE MAY ACTUALLY HAVE
A RELATIVELY DRY PERIOD AFTER 06 UTC. HOWEVER...THE 00 UTC GFS AND
EVEN THE 03 UTC SREF KEEP MORE STRATIFORM-BASED PRECIPITATION OVER
SOUTH CENTRAL MT AND NORTH CENTRAL WY RIGHT THROUGH THE NIGHT...SO
WE WERE CAUTIOUS ABOUT LOWERING POPS BELOW THE LIKELY THRESHOLD AT
THIS POINT. WE ALSO KEPT IN ISOLATED THUNDERSTORMS FOR MOST OF THE
AREA AFTER 06 UTC...BUT WE MIGHT BE ABLE TO DROP THAT MENTION WITH
LATER FORECASTS SINCE MUCAPE AND THE SREF THUNDERSTORM PROBABILITY
VALUES BOTH DWINDLE NOCTURNALLY.
ON SUN...A 500-HPA TROUGH IS EXPECTED TO CLOSE OFF...LIKELY ACROSS
WY...AND THAT SHOULD DRIVE A MORE STEADY RAIN EVENT ACROSS PART OR
EVEN ALL OF THE AREA. THIS IS THE POINT WHERE COMPLEX INTERACTIONS
OF SHORT WAVES AND CONVECTION WITHIN THE LARGER-SCALE TROUGH COULD
ULTIMATELY DICTATE WHERE AND HOW MUCH RAIN FALLS. WE INCREASED THE
POPS ONE MORE TIME THOUGH SO THAT THEY ARE CATEGORICAL FOR MUCH OF
THE AREA SINCE THERE IS FAIR AGREEMENT AMONG 00 UTC MODELS. LIKELY
AND CATEGORICAL POPS CONTINUE INTO SUN NIGHT.
HYDROLOGY-WISE...WE DECIDED TO LET GO OF THE FLASH FLOOD WATCH FOR
THE BURN SCAR AREAS WITH THIS FORECAST RELEASE. THE RAINFALL RATES
OVER THE NEXT FEW DAYS ARE NOT EXPECTED TO BE LARGE ENOUGH TO NEED
AN EXTENSION OF THE WATCH...THOUGH WE WILL CERTAINLY BE KEEPING AN
EYE ON THOSE BURN SCAR AREAS REGARDLESS. OTHERWISE...THERE WILL BE
AT LEAST MINOR RISES ON AREA RIVERS AND STREAMS IN THE COMING DAYS
IF THE FORECAST PRECIPITATION AMOUNTS COME TO FRUITION. HOWEVER...
NO FLOODING IS EXPECTED BECAUSE OUR VERY DRY SOILS WILL BE ABLE TO
EASILY ABSORB MUCH OF THE MOISTURE. SCHULTZ
.LONG TERM...VALID FOR MON...TUE...WED...THU...FRI...
THE EXTENDED PERIOD STARTS ON MONDAY AND MODEL DIFFERENCES MUDDY
THE WATERS ON TIMING OF PRECIPITATION TAPERING OFF OVER THE AREA.
BOTH MODELS MOVE THE UPPER LOW THAT WILL IMPACT THE AREA THIS
WEEKEND INTO EASTERN SOUTH DAKOTA BY 00Z TUESDAY. THE GFS BUILDS
THE RIDGE IN MUCH MORE AGGRESSIVELY AND SENDS WRAP AROUND ENERGY
AND MOISTURE SOUTH INTO WYOMING. THE ECMWF...HOWEVER...WAS SLOWER
WITH BUILDING HEIGHTS AND THIS ALLOWS ENERGY TO WRAP BACK INTO
EASTERN AND CENTRAL ZONES MONDAY. WILL SIDE WITH THE ECMWF AS THIS
WAS THE CONSENSUS OF SURROUNDING OFFICES AS OFTEN TIMES THESE
SLOW MOVING UPPER LOWS ARE SLOWER TO DRY OUT THAN MODELS EXPECT.
SHOULD GET DRYING CONDITIONS FOR TUESDAY AS THE RIDGE BUILDS IN
EARNEST. THE NEXT UPPER LOW...WHICH IS PROGGED TO BE QUITE A BIT
DEEPER THAN ITS PREDECESSOR...MOVES INLAND WEDNESDAY. ENERGY DOES
SWING AROUND THE UPPER LOW AND DRIVES ACROSS WESTERN AND CENTRAL
ZONES WEDNESDAY AND THURSDAY. LOW LEVEL WINDS WILL BE EASTERLY AND
THIS SHOULD ALLOW DEWPOINTS TO BE ON THE RISE. DRIER AIR WILL GET
PULLED INTO THE SYSTEM BUT THE GFS HAS BACKED OFF ON THIS FROM
YESTERDAY. CAPES SHOULD INCREASE WITH EASTERLY WINDS INCREASING
LOW LEVEL DEWPOINTS. RAISED POPS OVER WESTERN AND CENTRAL ZONES
FOR AFTERNOON AND EVENING CONVECTION WEDNESDAY AND THURSDAY. WILL
HAVE TO WATCH FOR A POTENTIAL DRY SLOT TO LIMIT CONVECTION...BUT
AS LONG AS THE MODELS KEEP THE WINDS EAST...NEED TO HAVE POPS IN
THERE. TEMPERATURES WILL MODERATE FROM THE LOWER 60S MONDAY TO THE
LOWER 70S TUESDAY AND HOLD AROUND THAT LEVEL THROUGH THE REST OF
THE WEEK. TWH
&&
.AVIATION...
SCATTERED SHOWERS AND THUNDERSTORMS THIS MORNING...MAINLY SOUTH
OF A KBIL TO KLVM LINE...CONTINUE TO EXPAND AND MOVE
NORTHEAST...AND WILL BECOME MORE WIDESPREAD THROUGH THE DAY. THE
PRECIP WILL CONTINUE TO MOVE SLOWLY NORTHEAST AND SHIFT OUT OF THE
AREA OVERNIGHT. SOME OF THE STORMS WILL CONTAIN MODERATE TO
BRIEFLY HEAVY RAINFALL AND COULD LOWER CONDITIONS TO MVFR. PATCHY
FOG REPORTED EAST OF A KBIL TO KSHR LINE IS LIFTING...AND SHOULD
CLEAR OUT BY LATE MORNING. MOUNTAINS WILL BE OBSCURED IN SHOWERS
AND CLOUDS THROUGHOUT THE DAY. AAG/TWH
&&
.PRELIMINARY POINT TEMP/POPS...
TDY SUN MON TUE WED THU FRI
-------------------------------------------------------
BIL 062 048/058 048/062 045/071 047/071 049/071 049/076
+/T 88/T 86/W 31/B 13/T 42/T 22/T
LVM 060 041/057 040/059 037/066 041/071 040/067 041/071
8/T 77/T 85/W 31/B 14/T 43/T 33/T
HDN 064 048/062 047/062 044/071 045/073 049/074 048/078
+/T 98/T 86/W 31/E 12/T 32/T 22/T
MLS 068 051/063 049/062 046/068 046/071 050/071 048/075
+/T +8/T 86/W 53/W 22/T 22/T 22/T
4BQ 069 048/059 047/060 043/063 044/071 048/071 047/075
+/T +8/T 87/W 53/W 11/B 22/T 21/B
BHK 068 048/060 047/060 043/061 043/067 048/067 048/070
8/T +8/T 86/W 53/W 21/B 22/T 22/T
SHR 065 047/056 043/057 040/064 040/073 046/072 045/076
9/T 67/T 86/W 42/W 12/T 32/T 22/T
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
000
FXUS65 KTFX 181518
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
918 AM MDT Sat May 18 2013
.UPDATE...
Very few updates this morning as current forecast is on track.
There will be breaks in the showers today with better coverage of
showers and isolated thunderstorms this afternoon, but overcast
skies will keep temperatures slightly cooler than seasonal
averages. MLV
&&
.AVIATION...
UPDATED 1125Z.
An upper level trough extending from the Great Basin area into the
Northern Rockies will make only slow eastward progress today...
keeping central and southwest MT under BKN-OVC skies with
intermittent periods of light rainshowers. There is also a slight
chance for isolated thunderstorms this aftn, but given their low
probability and spotty coverage did not include mention of any TS at
primary TAF sites today. Ceilings and visibilities should remain
VFR but brief MVFR/IFR conditions are possible near any
precipitation areas. Also, winds will be light across the region
today.
Waranauskas
&&
.HYDROLOGY...
Two upper level trofs, one moving through our region this weekend
and the other becoming stationary over the PACNW coast for much of
next week, will bring increased chances for rainfall over the next
several days. Though cooler temperatures will reduce snowmelt
slightly, the primary concern is that rain on the melting snowpack
will cause enhanced rises in stream/river levels. Most area rivers
are currently well below flood stage but a handful of sites are near
or approaching bankfull, so rainfall totals and river stage
forecasts will be closely monitored for significant changes and
impacts. Waranauskas
&&
.PREV DISCUSSION...
/ISSUED 525 AM MDT Sat May 18 2013/
Upper level trough extending from the Pacific NW through the Great
Basin will continue a slow progression east into the Rocky Mtn
region today, keeping the forecast area under a moist and somewhat
unstable SW flow aloft. Main focus for precipitation this morning
will be along an old/weakening deformation zone along the Hi-line
and over far SW MT ahead of the next incoming shortwave embedded
within the broader upper trough. Elsewhere, precipitation will be
limited to scattered light showers with patchy fog/drizzle through
early this morning. Daytime heating and the approaching shortwave
from the south should bring an increase in the coverage of showers
this afternoon and evening to most of the forecast area and an
isolated weak/brief thunderstorm or two cannot be ruled out,
however instability parameters are rather marginal. Sunday and
Monday, the upper trough emerges east of the Rockies with the
upper level circulation closing off as the trough undercuts an
upper ridge over central Canada. This results in a shift to more
northerly flow across the forecast area as the upper low center
tracks from Nebraska slowly northeast into the upper Midwest
through early next week. This should shift the focus for
widespread precipitation to north central MT, however all areas
will have some chance for showers through the period, especially
during the afternoon/evening time-frames. Temperatures will remain
close to seasonal averages today with slightly cooler conditions
on Sunday as the flow aloft turns to the north. Snow levels at or
above 8000 ft will limit any snow accumulation to the higher
peaks. Hoenisch
Monday Night through Saturday...Extended forecast period begins with
mostly quiet conditions as the upper level system that will cross
Montana this weekend will be moving into the Upper Midwest states
and a well-amplified high pressure ridge begins to settle in over
ern Montana and the Dakotas. Meanwhile, a second upper level trof
is forecast to swing through western Canada and form a closed low
pressure center over the PACNW coast by Tues eve. With the large
ridge remaining anchored thru the middle of the country, the Pacific
low essentially becomes stationary, drifting along the coast and
occasionally moving inland during the latter half of next week.
Minor shortwaves and accompanying moisture rotating around the
central low will bring intermittent periods of showers and isolated
thunderstorms each day from Wed onward. Forecast models are in
decent agreement that most parts of central/southwest MT will see
rain during this time, but precip amounts still look to be generally
light (0.10-0.15 inch or less) over the plains and valleys.
Rainfall totals are slightly higher (0.20-0.50 inch) over the
melting snowfields of the Rocky Mtn Front and Little Belt Mtns,
which gives concern for increased streamflows in creeks/rivers in
those areas. Persistent southerly flow aloft will allow
temperatures to stay close to typical seasonal values with highs in
the mid-60s to the low 70s each day, though that will be modified
quite a bit by a fair amount of cloud cover and the timing of the
shortwave passages.
Waranauskas
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 64 45 59 45 / 80 60 80 80
CTB 62 44 60 43 / 80 50 80 80
HLN 64 45 60 45 / 70 60 60 70
BZN 64 43 59 42 / 80 70 60 60
WEY 55 36 53 34 / 80 70 60 40
DLN 61 40 58 40 / 80 60 50 50
HVR 69 49 66 47 / 90 80 90 80
LWT 61 45 57 43 / 80 80 80 80
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
weather.gov/greatfalls
000
FXUS65 KTFX 181131
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
525 AM MDT Sat May 18 2013
AVIATION SECTION UPDATED
.DISCUSSION...
Upper level trough extending from the Pacific NW through the Great
Basin will continue a slow progression east into the Rocky Mtn
region today, keeping the forecast area under a moist and somewhat
unstable SW flow aloft. Main focus for precipitation this morning
will be along an old/weakening deformation zone along the Hi-line
and over far SW MT ahead of the next incoming shortwave embedded
within the broader upper trough. Elsewhere, precipitation will be
limited to scattered light showers with patchy fog/drizzle through
early this morning. Daytime heating and the approaching shortwave
from the south should bring an increase in the coverage of showers
this afternoon and evening to most of the forecast area and an
isolated weak/brief thunderstorm or two cannot be ruled out,
however instability parameters are rather marginal. Sunday and
Monday, the upper trough emerges east of the Rockies with the
upper level circulation closing off as the trough undercuts an
upper ridge over central Canada. This results in a shift to more
northerly flow across the forecast area as the upper low center
tracks from Nebraska slowly northeast into the upper Midwest
through early next week. This should shift the focus for
widespread precipitation to north central MT, however all areas
will have some chance for showers through the period, especially
during the afternoon/evening time-frames. Temperatures will remain
close to seasonal averages today with slightly cooler conditions
on Sunday as the flow aloft turns to the north. Snow levels at or
above 8000 ft will limit any snow accumulation to the higher
peaks. Hoenisch
Monday Night through Saturday...Extended forecast period begins with
mostly quiet conditions as the upper level system that will cross
Montana this weekend will be moving into the Upper Midwest states
and a well-amplified high pressure ridge begins to settle in over
ern Montana and the Dakotas. Meanwhile, a second upper level trof
is forecast to swing through western Canada and form a closed low
pressure center over the PACNW coast by Tues eve. With the large
ridge remaining anchored thru the middle of the country, the Pacific
low essentially becomes stationary, drifting along the coast and
occasionally moving inland during the latter half of next week.
Minor shortwaves and accompanying moisture rotating around the
central low will bring intermittent periods of showers and isolated
thunderstorms each day from Wed onward. Forecast models are in
decent agreement that most parts of central/southwest MT will see
rain during this time, but precip amounts still look to be generally
light (0.10-0.15 inch or less) over the plains and valleys.
Rainfall totals are slightly higher (0.20-0.50 inch) over the
melting snowfields of the Rocky Mtn Front and Little Belt Mtns,
which gives concern for increased streamflows in creeks/rivers in
those areas. Persistent southerly flow aloft will allow
temperatures to stay close to typical seasonal values with highs in
the mid-60s to the low 70s each day, though that will be modified
quite a bit by a fair amount of cloud cover and the timing of the
shortwave passages.
Waranauskas
&&
.AVIATION...
UPDATED 1125Z.
An upper level trough extending from the Great Basin area into the
Northern Rockies will make only slow eastward progress today...
keeping central and southwest MT under BKN-OVC skies with
intermittent periods of light rainshowers. There is also a slight
chance for isolated thunderstorms this aftn, but given their low
probability and spotty coverage did not include mention of any TS at
primary TAF sites today. Ceilings and visibilities should remain
VFR but brief MVFR/IFR conditions are possible near any
precipitation areas. Also, winds will be light across the region
today.
Waranauskas
&&
.HYDROLOGY...
Two upper level trofs, one moving through our region this weekend
and the other becoming stationary over the PACNW coast for much of
next week, will bring increased chances for rainfall over the next
several days. Though cooler temperatures will reduce snowmelt
slightly, the primary concern is that rain on the melting snowpack
will cause enhanced rises in stream/river levels. Most area rivers
are currently well below flood stage but a handful of sites are near
or approaching bankfull, so rainfall totals and river stage
forecasts will be closely monitored for significant changes and
impacts. Waranauskas
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 64 45 59 45 / 80 60 80 80
CTB 62 44 60 43 / 80 50 80 80
HLN 64 45 60 45 / 70 60 60 70
BZN 64 43 59 42 / 80 70 60 60
WEY 55 36 53 34 / 80 70 60 40
DLN 61 40 58 40 / 80 60 50 50
HVR 69 49 66 47 / 90 80 90 80
LWT 61 45 57 43 / 80 80 80 80
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...HOENISCH
LONG TERM...WARANAUSKAS
AVIATION...WARANAUSKAS
weather.gov/greatfalls
000
FXUS65 KTFX 181010
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
410 AM MDT Sat May 18 2013
.DISCUSSION...
Upper level trough extending from the Pacific NW through the Great
Basin will continue a slow progression east into the Rocky Mtn
region today, keeping the forecast area under a moist and somewhat
unstable SW flow aloft. Main focus for precipitation this morning
will be along an old/weakening deformation zone along the Hi-line
and over far SW MT ahead of the next incoming shortwave embedded
within the broader upper trough. Elsewhere, precipitation will be
limited to scattered light showers with patchy fog/drizzle through
early this morning. Daytime heating and the approaching shortwave
from the south should bring an increase in the coverage of showers
this afternoon and evening to most of the forecast area and an
isolated weak/brief thunderstorm or two cannot be ruled out,
however instability parameters are rather marginal. Sunday and
Monday, the upper trough emerges east of the Rockies with the
upper level circulation closing off as the trough undercuts an
upper ridge over central Canada. This results in a shift to more
northerly flow across the forecast area as the upper low center
tracks from Nebraska slowly northeast into the upper Midwest
through early next week. This should shift the focus for
widespread precipitation to north central MT, however all areas
will have some chance for showers through the period, especially
during the afternoon/evening time-frames. Temperatures will remain
close to seasonal averages today with slightly cooler conditions
on Sunday as the flow aloft turns to the north. Snow levels at or
above 8000 ft will limit any snow accumulation to the higher
peaks. Hoenisch
Monday Night through Saturday...Extended forecast period begins with
mostly quiet conditions as the upper level system that will cross
Montana this weekend will be moving into the Upper Midwest states
and a well-amplified high pressure ridge begins to settle in over
ern Montana and the Dakotas. Meanwhile, a second upper level trof
is forecast to swing through western Canada and form a closed low
pressure center over the PACNW coast by Tues eve. With the large
ridge remaining anchored thru the middle of the country, the Pacific
low essentially becomes stationary, drifting along the coast and
occasionally moving inland during the latter half of next week.
Minor shortwaves and accompanying moisture rotating around the
central low will bring intermittent periods of showers and isolated
thunderstorms each day from Wed onward. Forecast models are in
decent agreement that most parts of central/southwest MT will see
rain during this time, but precip amounts still look to be generally
light (0.10-0.15 inch or less) over the plains and valleys.
Rainfall totals are slightly higher (0.20-0.50 inch) over the
melting snowfields of the Rocky Mtn Front and Little Belt Mtns,
which gives concern for increased streamflows in creeks/rivers in
those areas. Persistent southerly flow aloft will allow
temperatures to stay close to typical seasonal values with highs in
the mid-60s to the low 70s each day, though that will be modified
quite a bit by a fair amount of cloud cover and the timing of the
shortwave passages.
Waranauskas
&&
.AVIATION...
UPDATED 05Z.
Moist unstable flow aloft will continue across the region for the
next 24 hours as the upper-level trough slowly progresses into the
Western US through the TAF period. Showers will remain in the area
throughout the TAF period with some breaks between individual
showers...however widespread precipitation is expected throughout
the time frame.
&&
.HYDROLOGY...
Two upper level trofs, one moving through our region this weekend
and the other becoming stationary over the PACNW coast for much of
next week, will bring increased chances for rainfall over the next
several days. Though cooler temperatures will reduce snowmelt
slightly, the primary concern is that rain on the melting snowpack
will cause enhanced rises in stream/river levels. Most area rivers
are currently well below flood stage but a handful of sites are near
or approaching bankfull, so rainfall totals and river stage
forecasts will be closely monitored for significant changes and
impacts. Waranauskas
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 64 45 59 45 / 80 60 80 80
CTB 62 44 60 43 / 80 50 80 80
HLN 64 45 60 45 / 70 60 60 70
BZN 64 43 59 42 / 80 70 60 60
WEY 55 36 53 34 / 80 70 60 40
DLN 61 40 58 40 / 80 60 50 50
HVR 69 49 66 47 / 90 80 90 80
LWT 61 45 57 43 / 80 80 80 80
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...HOENISCH
LONG TERM...WARANAUSKAS
AVIATION...WARANAUSKAS
weather.gov/greatfalls
000
FXUS65 KGGW 180952
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
352 AM MDT SAT MAY 18 2013
.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH MONDAY...
TODAY THROUGH MONDAY...MAIN CONCERN WILL BE THE CONTINUATION OF
WET WEATHER ACROSS NORTHEAST MONTANA. CURRENT RADAR OBSERVATIONS
EARLY THIS MORNING ARE SHOWING A RATHER EXPANSIVE AREA OF SHOWER
ACTIVITY ACROSS THE CWA. SOME 40-50 DBZ REFLECTIVITY HAS BEEN
OCCURRING FROM TIME TO TIME IN VERY ISOLATED LOCATIONS AND SO
CANNOT RULE OUT A RUMBLE OF THUNDER THIS MORNING.
MODELS ARE IN EXCELLENT AGREEMENT WITH THE OVERALL SYNOPTIC
PATTERN KEEPING IN AN UPPER LEVEL TROUGH PERSISTING ACROSS THE CWA
WHICH WILL PROVIDE A CONTINUATION OF UNSETTLED WEATHER CONDITIONS.
HOWEVER...THERE ARE NOTABLE DIFFERENCES FROM THE MODELS IN THE DETAILS
AND HANDLING OF MESOSCALE CONVECTION THAT DEVELOPS. THE GFS IN
PARTICULAR HAS NOT BEEN PERFORMING WELL IN THE PLACEMENT OF QPF
WITH RECENT RAIN SHOWER ACTIVITY AND THEREFORE HAVE DISCOUNTED IT
FOR THE SHORT TERM FORECAST PERIOD. THE 00Z ECMWF AND THE LATEST
HRRR HAVE SHOWN TO HAVE A PRETTY GOOD HANDLE ON THE OVERALL
SITUATION AND LEANED WITH A COMPROMISE OF THEIR SOLUTIONS IN LARGE
PART FOR THE FORECAST. IN A NUTSHELL...UPPER LEVEL SHORTWAVE
FEATURES WILL PROPAGATE THROUGH SOUTHWEST FLOW ALOFT WHICH ALONG
WITH UPPER LEVEL DIFFLUENCE WILL HELP FORCE VERTICAL ASCENT. A
SURFACE LOW PRESSURE WILL ALSO SIT AND SPIN ACROSS THE DAKOTAS
THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK WHICH WILL CONTINUE
TO PROVIDE MOIST EASTERLY FLOW INTO NORTHEAST MONTANA. GIVEN THESE
CIRCUMSTANCES...FEEL VERY CONFIDENT IN WIDESPREAD MEASURABLE
RAINFALL ACCUMULATIONS.
THE CHALLENGE WITH THIS FORECAST WILL BE DETERMINING WHERE THE
HEAVIEST AMOUNTS OF RAINFALL WILL OCCUR...WHICH WILL LARGELY
DEPEND UPON MESOSCALE DETAILS THAT ARE DIFFICULT TO PINPOINT WITH
MUCH CONFIDENCE AT THIS TIME. AREAS WITH HEAVIEST RAINFALL MAY
CERTAINLY PICK UP OVER AN INCH OF RAINFALL...IF NOT MORE...THROUGH
EARLY NEXT WEEK. GIVEN THESE ARGUMENTS...WILL GO WITH CATEGORICAL
POPS IN MOST PLACES THROUGH SUNDAY NIGHT AND TAPER TO LIKELY POPS
ON MONDAY AS THE UPPER TROUGH BEGINS TO TRANSLATE EASTWARD AND THE
SURFACE LOW EXITS THE DAKOTAS AND HEADS FOR SW MN AND NW IA. NAM
BUFR SOUNDINGS CONTINUE TO INDICATE LI READINGS AROUND 0 OR
SLIGHTLY NEGATIVE ACROSS PARTS OF THE CWA AT TIMES GOING INTO
TONIGHT...AND INDICATE SMALL AMOUNTS OF CAPE AND SOME INSTABILITY.
DECIDED TO KEEP A SLIGHT MENTION FOR THUNDER IN THE GRIDS GIVEN
THESE ARGUMENTS. NO LARGE SWINGS IN TEMPERATURES ARE EXPECTED
THROUGH THE SHORT TERM SINCE THE OVERALL PATTERN WILL REMAIN
RATHER STATIC. THEREFORE WILL EXPECT SEASONAL HIGHS AND LOWS
THROUGH EARLY NEXT WEEK. MALIAWCO
.LONG TERM...MONDAY NIGHT THROUGH SATURDAY...
THE EXTENDED FORECAST BEGINS MONDAY NIGHT WITH AN UPPER LOW
EXITING INTO THE UPPER MISSISSIPPI RIVER VALLEY AND WEAK RIDGING
BUILDING INTO NORTHEASTERN MONTANA.
BY WEDNESDAY MORNING ANOTHER UPPER LOW MOVES IN OVER THE PACIFIC
NORTHWEST SETTING UP DI-FLUENT SOUTHWEST FLOW ALOFT OVER THE AREA
THROUGH THE END OF THE EXTENDED.
THIS WILL CONTINUE THE COOLISH TEMPERATURES DURING THE DAY AND
NEAR NORMAL TEMPERATURES AT NIGHT. PRECIPITATION CHANCES SHOULD
RANGE SLIGHTLY ABOVE NORMAL... HOWEVER PIN POINTING ANY BETTER
DAYS THAN OTHERS WILL BE VERY HARD.
ENSEMBLES OF THE GFS AND EC SHOW HIGH CONFIDENCE IN AN UPPER LOW
OVER THE PACIFIC NORTHWEST...HOWEVER DO HAVE TROUBLE KEEPING THE
DAY TO DAY PLACEMENT OF THE UPPER LOW THE SAME. RMOP IS PRETTY
GOOD FOR UPPER LOWS OVER THE PACIFIC NORTHWEST. MODERATE TO HIGH
CONFIDENCE ON THE PATTERN. HOWEVER THE PATTERN IS MORE SHOWERY IN
NATURE NOT ALLOWING FOR THE CONFIDENCE TO DOUBLE OF CLIMO POPS AT
THIS TIME. PROTON
&&
.AVIATION...
VFR WITH PERIODS OF MVFR CAN BE EXPECTED THROUGH THE PERIOD AT ALL
TERMINALS.
SOUTHWEST FLOW ALOFT AND MOIST EAST TO SOUTHEAST WILL KEEP SKIES
BROKEN TO OVERCAST. CEILINGS WILL BE TRICKY... GUIDANCE HAS A
SPLIT WITH ONE GOING FOR SOLID MVFR...THE OTHER SOLID VFR. WILL GO
WITH THE PREDOMINATE OF VFR AND PERIODS OF MVFR MAINLY FOR MORNING
LOWER CEILINGS AND ANY AFTERNOON CBS THAT FORM. PROTON
&&
.HYDROLOGY...
THE NEXT FEW DAYS WILL BE RATHER WET AS AN UPPER-LEVEL TROUGH
AFFECTS THE AREA. SEVERAL DISTURBANCES ASSOCIATED WITH THIS TROUGH
WILL PASS THROUGH WHICH WILL KEEP CHANCES FOR RAIN WITH SOME
THUNDERSTORMS THROUGH EARLY NEXT WEEK. MODEL GUIDANCE DEPICTS HIGH
AMOUNTS OF MOISTURE WITH THIS SYSTEM. AT THIS POINT THE
ENVIRONMENT LOOKS FAVORABLE FOR SLOW- MOVING STORMS WITH HIGHER
PRECIPITATION IN LOCALIZED AREAS.
MOST OF THE BASINS IN NORTHEAST MONTANA WILL BE ABLE TO ACCOMMODATE
THIS AMOUNT OF MOISTURE... AT LEAST EARLY ON IN THE EVENT. THERE IS
SOME CONCERN FOR RAPIDLY RISING STREAMS AND LOCALIZED URBAN
FLOODING AS THE EVENT PERSISTS. SOME FLOODING MAY BECOME AN
ISSUE... ESPECIALLY FOR THE EASTERN AND SOUTHERN COUNTIES WHERE
THE POTENTIAL FOR STRONGER THUNDERSTORMS IS HIGHER.
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
WEATHER.GOV/GLASGOW
000
FXUS65 KMSO 180941
AFDMSO
Area Forecast Discussion
National Weather Service Missoula MT
341 AM MDT Sat May 18 2013
.DISCUSSION...Rain showers will continue across the Northern
Rockies, but a few breaks will also occur throughout the day.
Showers will be widespread in coverage, with periods of heavier
rainfall followed by periods of lighter showers. This pattern will
continue overnight and into Sunday as well, keeping conditions
rather dull and dreary. While most places will see rain at some
point today, the best focus of moisture will cover southwest
Montana and locations closest to Glacier National Park. Snow
showers may provide a light coating of new snowfall in the higher
terrain of GNP.
Temperatures on the whole will be a few degrees warmer than
Friday, but still much cooler than normal for mid May. Depending
on how often the sun breaks through the clouds, some parts of the
day could feel warmer and more humid as a result. Very similar
trends are expected through Monday, with each day warming a few
degrees.
Tuesday through Wednesday...Forecast confidence remains high for a
deepening closed low system developing over the Pacific Northwest.
This low system remains nearly stationary giving it plenty of time
to circulate warm, unstable and increasingly moist air up from the
south and into the Northern Rockies. Thunderstorms are becoming a
more prominent forecast element, as well as surges of localized
moderate to heavy rainfall. Glacier National Park and possibly the
Bob Marshall Wilderness area could be a main focal point for some
of the heaviest rainfall Wednesday and Wednesday night.
Thursday and Friday...Forecast models suggest that the main low
circulation remains over the Pacific Northwest, but differ
considerably as to the location of heaviest rainfall. Much of this
uncertainty can be attributed to how each model handles the low
system. The GFS maintains a single low center, while the ECMWF
splits it into two separate low centers, dumbelling around each
other which alters the position and timing of precipitation into
the region. The evolution of the low system will continued to
monitored and hopefully the models help paint a clearer picture of
what we can expect down the road for Memorial weekend.
&&
.AVIATION...An upper level trough of low pressure will maintain a
moist, unstable environment over the Northern Rockies region today
and tonight. Numerous rain showers and lower ceilings will be
impacting most airfields across north-central Idaho and western
Montana. Mountain obscurement will be commonplace.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&
$$
Follow us on Facebook and Twitter!
https://www.facebook.com/US.NationalWeatherService.Missoula.gov
https://www.twitter.com/NWSMissoula
000
FXUS65 KBYZ 180935
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
335 AM MDT SAT MAY 18 2013
.SHORT TERM...VALID FOR TDY AND SUN...
RAINFALL TOTALING AN INCH OR MORE STILL LOOKS LIKE A GOOD BET OVER
THE NEXT FEW DAYS IN MANY AREAS. HOWEVER...THE 500-HPA TROUGH THAT
IS SET TO DRIVE ONE OF THE BETTER PRECIPITATION EVENTS WE HAVE HAD
IN A LONG TIME IS SURPRISING COMPLEX...SO SOME UNCERTAINTY EXISTS.
TODAY...THE MID-LEVEL SHORT WAVE TROUGH CENTERED NEAR 700 HPA THAT
IS SEEN ENTERING WESTERN WY ON 09 UTC MOISTURE CHANNEL IMAGES WILL
MOVE INTO SOUTHERN MT. THE ECMWF HAS BEEN THE MOST CONSISTENT WITH
BRINGING THIS BATCH OF FORCING INTO THE AREA IN THE LAST FEW DAYS.
ITS 00 UTC RUN CONTINUES THIS THEME...GENERATING CONVECTION ACROSS
MUCH OF THE AREA AFTER 18 UTC...WITH QPF AMOUNTS OF A QUARTER TO A
HALF INCH. THE 00 UTC GFS HAS FINALLY PICKED UP ON THIS SHORT WAVE
TOO...SO OUR CONFIDENCE IN PRECIPITATION HAS INCREASED ENOUGH THAT
WE HAVE CHOSEN TO ADVERTISE 90 TO 100 PERCENT POPS AFTER 18 UTC IN
THE BILLINGS...SHERIDAN...MILES CITY...AND BROADUS AREAS. THE 700-
500 HPA LAPSE RATES ARE MODEST AROUND 6 C/KM...BUT THERE IS ENOUGH
INSTABILITY /POCKETS OF MUCAPE UP TO 500 J/KG/ TO GENERATE THUNDER
AS WELL. CALIBRATED THUNDERSTORM PROBABILITIES OFF THE 03 UTC SREF
JUMP UP INTO THE 40 AND 50 PERCENT RANGE AFTER 18 UTC AS WELL. THE
SEVERE RISK IS NEGLIGIBLE THOUGH GIVEN THE EXPECTED INSTABILITY. A
CAUTIONARY NOTE ABOUT THE POP FORECAST IS THAT MANY WRF-BASED HIGH
RESOLUTION MODELS FROM 00 UTC CLUSTER CONVECTION FURTHER SOUTHEAST
FROM SHERIDAN TOWARD BROADUS...WHICH MAY ACTUALLY SUPPRESS SOME OF
THE PRECIPITATION FURTHER NORTH IN PLACES LIKE BILLINGS. NOTE THAT
WE ALSO DECIDED TO CARRY ONLY CHANCE POPS IN MANY PLACES BEFORE 18
UTC BASED ON UPSTREAM TRENDS AND RECENT RAP AND HRRR OUTPUT.
TONIGHT...WE CONTINUED LEANING ON THE 00 UTC ECMWF SOLUTION DURING
THE EVENING...WITH A CONCENTRATED AREA OF CATEGORICAL POPS FOR THE
PLAINS OF SOUTH CENTRAL AND SOUTHEASTERN MT BEFORE 06 UTC. WE THEN
LET POPS FALL BACK A BIT AFTER MIDNIGHT IN MANY AREAS SINCE 1/ THE
DIURNALLY-DRIVEN CONVECTION SHOULD DIMINISH WITH SUNSET...AND 2/ A
BREAK IN FORCING SHOULD TAKE PLACE AS THE 700-HPA SHORT WAVE MOVES
OUT AND/OR WEAKENS. IF THE ECMWF IS CORRECT...WE MAY ACTUALLY HAVE
A RELATIVELY DRY PERIOD AFTER 06 UTC. HOWEVER...THE 00 UTC GFS AND
EVEN THE 03 UTC SREF KEEP MORE STRATIFORM-BASED PRECIPITATION OVER
SOUTH CENTRAL MT AND NORTH CENTRAL WY RIGHT THROUGH THE NIGHT...SO
WE WERE CAUTIOUS ABOUT LOWERING POPS BELOW THE LIKELY THRESHOLD AT
THIS POINT. WE ALSO KEPT IN ISOLATED THUNDERSTORMS FOR MOST OF THE
AREA AFTER 06 UTC...BUT WE MIGHT BE ABLE TO DROP THAT MENTION WITH
LATER FORECASTS SINCE MUCAPE AND THE SREF THUNDERSTORM PROBABILITY
VALUES BOTH DWINDLE NOCTURNALLY.
ON SUN...A 500-HPA TROUGH IS EXPECTED TO CLOSE OFF...LIKELY ACROSS
WY...AND THAT SHOULD DRIVE A MORE STEADY RAIN EVENT ACROSS PART OR
EVEN ALL OF THE AREA. THIS IS THE POINT WHERE COMPLEX INTERACTIONS
OF SHORT WAVES AND CONVECTION WITHIN THE LARGER-SCALE TROUGH COULD
ULTIMATELY DICTATE WHERE AND HOW MUCH RAIN FALLS. WE INCREASED THE
POPS ONE MORE TIME THOUGH SO THAT THEY ARE CATEGORICAL FOR MUCH OF
THE AREA SINCE THERE IS FAIR AGREEMENT AMONG 00 UTC MODELS. LIKELY
AND CATEGORICAL POPS CONTINUE INTO SUN NIGHT.
HYDROLOGY-WISE...WE DECIDED TO LET GO OF THE FLASH FLOOD WATCH FOR
THE BURN SCAR AREAS WITH THIS FORECAST RELEASE. THE RAINFALL RATES
OVER THE NEXT FEW DAYS ARE NOT EXPECTED TO BE LARGE ENOUGH TO NEED
AN EXTENSION OF THE WATCH...THOUGH WE WILL CERTAINLY BE KEEPING AN
EYE ON THOSE BURN SCAR AREAS REGARDLESS. OTHERWISE...THERE WILL BE
AT LEAST MINOR RISES ON AREA RIVERS AND STREAMS IN THE COMING DAYS
IF THE FORECAST PRECIPITATION AMOUNTS COME TO FRUITION. HOWEVER...
NO FLOODING IS EXPECTED BECAUSE OUR VERY DRY SOILS WILL BE ABLE TO
EASILY ABSORB MUCH OF THE MOISTURE. SCHULTZ
.LONG TERM...VALID FOR MON...TUE...WED...THU...FRI...
THE EXTENDED PERIOD STARTS ON MONDAY AND MODEL DIFFERENCES MUDDY
THE WATERS ON TIMING OF PRECIPITATION TAPERING OFF OVER THE AREA.
BOTH MODELS MOVE THE UPPER LOW THAT WILL IMPACT THE AREA THIS
WEEKEND INTO EASTERN SOUTH DAKOTA BY 00Z TUESDAY. THE GFS BUILDS
THE RIDGE IN MUCH MORE AGGRESSIVELY AND SENDS WRAP AROUND ENERGY
AND MOISTURE SOUTH INTO WYOMING. THE ECMWF...HOWEVER...WAS SLOWER
WITH BUILDING HEIGHTS AND THIS ALLOWS ENERGY TO WRAP BACK INTO
EASTERN AND CENTRAL ZONES MONDAY. WILL SIDE WITH THE ECMWF AS THIS
WAS THE CONSENSUS OF SURROUNDING OFFICES AS OFTEN TIMES THESE
SLOW MOVING UPPER LOWS ARE SLOWER TO DRY OUT THAN MODELS EXPECT.
SHOULD GET DRYING CONDITIONS FOR TUESDAY AS THE RIDGE BUILDS IN
EARNEST. THE NEXT UPPER LOW...WHICH IS PROGGED TO BE QUITE A BIT
DEEPER THAN ITS PREDECESSOR...MOVES INLAND WEDNESDAY. ENERGY DOES
SWING AROUND THE UPPER LOW AND DRIVES ACROSS WESTERN AND CENTRAL
ZONES WEDNESDAY AND THURSDAY. LOW LEVEL WINDS WILL BE EASTERLY AND
THIS SHOULD ALLOW DEWPOINTS TO BE ON THE RISE. DRIER AIR WILL GET
PULLED INTO THE SYSTEM BUT THE GFS HAS BACKED OFF ON THIS FROM
YESTERDAY. CAPES SHOULD INCREASE WITH EASTERLY WINDS INCREASING
LOW LEVEL DEWPOINTS. RAISED POPS OVER WESTERN AND CENTRAL ZONES
FOR AFTERNOON AND EVENING CONVECTION WEDNESDAY AND THURSDAY. WILL
HAVE TO WATCH FOR A POTENTIAL DRY SLOT TO LIMIT CONVECTION...BUT
AS LONG AS THE MODELS KEEP THE WINDS EAST...NEED TO HAVE POPS IN
THERE. TEMPERATURES WILL MODERATE FROM THE LOWER 60S MONDAY TO THE
LOWER 70S TUESDAY AND HOLD AROUND THAT LEVEL THROUGH THE REST OF
THE WEEK. TWH
&&
.AVIATION...
SCATTERED SHOWERS AND THUNDERSTORMS THIS MORNING WILL BECOME MORE
WIDESPREAD BY EARLY AFTERNOON. THE PRECIPITATION WILL MOVE SLOWLY
NORTHEAST AND SHIFT OUT OF THE AREA OVERNIGHT. SOME OF THE STORMS
WILL CONTAIN MODERATE TO BRIEFLY HEAVY RAINFALL AND COULD LOWER
CONDITIONS TO MVFR. PATCHY FOG WILL BE POSSIBLE THIS MORNING EAST
OF A BILLINGS TO SHERIDAN LINE...WITH CONDITIONS DROPPING TO MVFR
LOCALLY. THE FOG WILL LIFT BY LATE MORNING. MOUNTAINS WILL BE
OBSCURED IN SHOWERS AND CLOUDS. TWH
&&
.PRELIMINARY POINT TEMP/POPS...
TDY SUN MON TUE WED THU FRI
-------------------------------------------------------
BIL 062 048/058 048/062 045/071 047/071 049/071 049/076
+/T 88/T 86/W 31/B 13/T 42/T 22/T
LVM 060 041/057 040/059 037/066 041/071 040/067 041/071
8/T 77/T 85/W 31/B 14/T 43/T 33/T
HDN 064 048/062 047/062 044/071 045/073 049/074 048/078
+/T 98/T 86/W 31/E 12/T 32/T 22/T
MLS 068 051/063 049/062 046/068 046/071 050/071 048/075
+/T +8/T 86/W 53/W 22/T 22/T 22/T
4BQ 069 048/059 047/060 043/063 044/071 048/071 047/075
+/T +8/T 87/W 53/W 11/B 22/T 21/B
BHK 068 048/060 047/060 043/061 043/067 048/067 048/070
8/T +8/T 86/W 53/W 21/B 22/T 22/T
SHR 065 047/056 043/057 040/064 040/073 046/072 045/076
9/T 67/T 86/W 42/W 12/T 32/T 22/T
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
000
FXUS65 KTFX 180510
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1100 PM MDT Fri May 17 2013
...UPDATE TO AVIATION...
.DISCUSSION...
Update forthcoming. Have made some minor adjustments to the grids to
better align with neighboring offices. Upper trof continues to move
toward the area with plenty of moisture and instability moving into
the state ahead of the trof. Models continue to indicate some breaks
in the showers from time to time but timing of these breaks will be
difficult. Unsettled showery conditions will persist through the
weekend. Overnight temperatures look good with overcast conditions
keeping readings from dropping precipitously. Emanuel
&&
.AVIATION...
UPDATED 05Z.
Moist unstable flow aloft will continue across the region for the
next 24 hours as the upper-level trough slowly progresses into the
Western US through the TAF period. Showers will remain in the area
throughout the TAF period with some breaks between individual
showers...however widespread precipitation is expected throughout
the time frame.
&&
.PREV DISCUSSION...Issued 255 PM MDT Fri May 17 2013
Tonight through Sunday...Rain and isolated embedded thunderstorms
will continue to develop this evening as an upper-level trough of
low pressure pushes into the Northern Rockies. Short-range models
continue to show differences in the track of each shortwave moving
across the forecast area. While precipitation will continue to
develop over north-central Montana, across southwest Montana
precipitation will taper tonight. Partial clearing in this area
may allow for fog to develop, however confidence is not high given
the amount of cloud cover expected. There will be breaks in
precipitation throughout the weekend with the greatest
concentration of showers and thunderstorms during the afternoon
when instability increases. Cooler, Canadian air will keep snow
levels lower Saturday and Sunday, especially along the Rocky Mountain
Front, though any accumulating snow will be well above pass level
and precipitation should remain all rain at most mountain passes.
The only exception is for Kings Hill and Chief Joseph passes where
a mix of rain and snow showers are possible, but little or no snow
accumulation is expected. The main trough axis will move over the
Northern Rockies on Sunday and as better lift and northerly flow
wraps in on the northeast side of the trough, precipitation will
become more widespread and steadier over north-central Montana.
Over southwest Montana, precipitation will remain scattered.
Temperatures will remain below seasonal averages through the
period. MLV
Monday night through Saturday...Medium range models are in fair
agreement overall through next week in the large scale, depicting a
relatively unsettled and highly amplified pattern with one closed
upper level low drifting from the central Rockies into the upper
Midwest Sunday night and Monday while another drops south along the
west coast, impacting the region in the middle to end of next week.
The circulation around the broad upper low drifting east from WY to
the Dakotas Sunday night/Monday will maintain a moist northerly flow
over the region with widespread precipitation likely Sunday night,
especially over portions of North Central Mt along and adjacent to
the Rocky Mtn Front and Central MT Mtns. Weak/transient upper level
ridging between systems drifts across the northern Rockies and MT
Monday night through Tuesday, bringing a period of relatively
dry/quiet conditions. While medium range models agree on the idea of
a deep and slow moving upper low along the west coast during Wed
thru Friday of next week, gradually working inland next weekend,
details of shortwave energy placement and timing are not yet
resolved. The first shortwave rotates up through western MT Wed/Wed
night, bringing a good chance for precipitation across much of the
forecast area. Later in the week into next weekend, the overall
pattern looks to be conducive to increasingly active convective
shower/thunderstorm development as flow aloft turns southerly with
with low level east to southeast flow importing moisture into North
Central and eastern MT. Hoenisch
&&
.HYDROLOGY...
A broad, upper level low pressure trof will bring cooler
temperatures to the region and this will moderate the melting of
the snowpack. However, the increased chance of precipitation will
also increase the chance for further rises in rivers and streams
across much of north central and southwest Montana through the
upcoming weekend. In addition, rain falling on recent burn areas
can cause rapid runoff and possible debris flows.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 45 64 44 60 / 70 80 70 70
CTB 43 62 42 60 / 60 70 70 60
HLN 44 65 43 61 / 70 80 70 70
BZN 40 65 40 60 / 80 80 80 70
WEY 40 57 37 55 / 60 80 70 60
DLN 40 62 38 59 / 80 80 80 60
HVR 47 69 47 66 / 60 70 70 70
LWT 44 61 43 57 / 70 80 80 70
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
weather.gov/greatfalls
000
FXUS65 KTFX 180306
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
855 PM MDT Fri May 17 2013
.DISCUSSION...
Update forthcoming. Have made some minor adjustments to the grids to
better align with neighboring offices. Upper trof continues to move
toward the area with plenty of moisture and instability moving into
the state ahead of the trof. Models continue to indicate some breaks
in the showers from time to time but timing of these breaks will be
difficult. Unsettled showery conditions will persist through the
weekend. Overnight temperatures look good with overcast conditions
keeping readings from dropping precipitously. Emanuel
&&
.AVIATION...
UPDATED 00Z.
Moist unstable flow aloft will continue across the region for the
next 24 hours as the upper-level trough slowly progresses into the
Western US through Saturday. Showers will remain in the area
throughout the TAF period with some breaks between individual
showers...however widespread precipitation is expected throughout
the time frame.
&&
.PREV DISCUSSION...Issued 255 PM MDT Fri May 17 2013
Tonight through Sunday...Rain and isolated embedded thunderstorms
will continue to develop this evening as an upper-level trough of
low pressure pushes into the Northern Rockies. Short-range models
continue to show differences in the track of each shortwave moving
across the forecast area. While precipitation will continue to
develop over north-central Montana, across southwest Montana
precipitation will taper tonight. Partial clearing in this area
may allow for fog to develop, however confidence is not high given
the amount of cloud cover expected. There will be breaks in
precipitation throughout the weekend with the greatest
concentration of showers and thunderstorms during the afternoon
when instability increases. Cooler, Canadian air will keep snow
levels lower Saturday and Sunday, especially along the Rocky Mountain
Front, though any accumulating snow will be well above pass level
and precipitation should remain all rain at most mountain passes.
The only exception is for Kings Hill and Chief Joseph passes where
a mix of rain and snow showers are possible, but little or no snow
accumulation is expected. The main trough axis will move over the
Northern Rockies on Sunday and as better lift and northerly flow
wraps in on the northeast side of the trough, precipitation will
become more widespread and steadier over north-central Montana.
Over southwest Montana, precipitation will remain scattered.
Temperatures will remain below seasonal averages through the
period. MLV
Monday night through Saturday...Medium range models are in fair
agreement overall through next week in the large scale, depicting a
relatively unsettled and highly amplified pattern with one closed
upper level low drifting from the central Rockies into the upper
Midwest Sunday night and Monday while another drops south along the
west coast, impacting the region in the middle to end of next week.
The circulation around the broad upper low drifting east from WY to
the Dakotas Sunday night/Monday will maintain a moist northerly flow
over the region with widespread precipitation likely Sunday night,
especially over portions of North Central Mt along and adjacent to
the Rocky Mtn Front and Central MT Mtns. Weak/transient upper level
ridging between systems drifts across the northern Rockies and MT
Monday night through Tuesday, bringing a period of relatively
dry/quiet conditions. While medium range models agree on the idea of
a deep and slow moving upper low along the west coast during Wed
thru Friday of next week, gradually working inland next weekend,
details of shortwave energy placement and timing are not yet
resolved. The first shortwave rotates up through western MT Wed/Wed
night, bringing a good chance for precipitation across much of the
forecast area. Later in the week into next weekend, the overall
pattern looks to be conducive to increasingly active convective
shower/thunderstorm development as flow aloft turns southerly with
with low level east to southeast flow importing moisture into North
Central and eastern MT. Hoenisch
&&
.HYDROLOGY...
A broad, upper level low pressure trof will bring cooler
temperatures to the region and this will moderate the melting of
the snowpack. However, the increased chance of precipitation will
also increase the chance for further rises in rivers and streams
across much of north central and southwest Montana through the
upcoming weekend. In addition, rain falling on recent burn areas
can cause rapid runoff and possible debris flows.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 45 64 44 60 / 70 80 70 70
CTB 43 62 42 60 / 60 70 70 60
HLN 44 65 43 61 / 70 80 70 70
BZN 40 65 40 60 / 80 80 80 70
WEY 40 57 37 55 / 60 80 70 60
DLN 40 62 38 59 / 80 80 80 60
HVR 47 69 47 66 / 60 70 70 70
LWT 44 61 43 57 / 70 80 80 70
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
weather.gov/greatfalls
000
FXUS65 KBYZ 180305
AFDBYZ
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
905 PM MDT FRI MAY 17 2013
.UPDATE...
MUCH OF THE PRECIPITATION HAS LIFTED NORTH/NORTHEAST ACROSS OUR
FORECAST AREA THIS EVENING LEAVING RAIN COOLED AIR IN ITS PLACE
WITH LOW LEVEL LAPSE RATES DROPPING BELOW 6 C/KM. HOWEVER...ANOTHER
SLUG OF QG FORCING IS MOVING ACROSS SE IDAHO AND NW UTAH AND
SHOULD LEAD TO ANOTHER ROUND OF SHOWERS AND THUNDERSHOWERS/STORMS
BY TOMORROW MORNING. I HAVE LOWERED POPS ACROSS MUCH OF THE AREA
THE REST OF THE NIGHT...LEAVING SOME HIGHER CHANCE POPS IN THE
WEST OVER AND NEAR THE HIGH COUNTRY WHERE SOME ISENTROPIC LIFT IS
GENERATING SOME SHOWERS. ADDED A MENTION OF PATCHY FOG OVERNIGHT
DUE TO ABUNDANCE OF LOW LEVEL MOISTURE AND NARROW DEWPOINT
DEPRESSIONS.
WILL LEAVE FLASH FLOOD WATCH ALONE FOR NOW AS I SUSPECT WE WILL
NEED TO EXTEND IT AS MODELS CONTINUE TO GENERATE IMPRESSIVE QPF
FOR THE WEEKEND WITH EMBEDDED THUNDERSTORMS OVER THE BURN SCARS
STILL POSSIBLE. BT
&&
.SHORT TERM...VALID FOR SAT AND SUN...
A MOIST AND SLOW MOVING UPPER TROUGH OF LOW PRESSURE WILL BRING
MUCH NEEDED PRECIPITATION TO THE ENTIRE FORECAST AREA TONIGHT
THROUGH SUNDAY.
TONIGHT...CONVECTION DEVELOPING OVER NORTHWEST WYOMING LATE THIS
AFTERNOON IN RESPONSE TO 70 KT JET STREAK MOVING TOWARD OUR
SOUTHWEST ZONES. THIS JET WILL BRING INCREASING LIFT TO OUR
CENTRAL AND EASTERN ZONES THIS EVENING. HRRR/SSEO ALONG WITH THE
NAM12 ARE INDICATING STRONGEST CONVECTION WILL LIKELY DEVELOP OVER
AN AREA FROM EASTERN SHERIDAN COUNTY TO EKALAKA LATE THIS
AFTERNOON INTO THIS EVENING. HAVE RAISED POPS FOR TONIGHT AND WILL
KEEP MENTION OF A FEW SEVERE THUNDERSTORMS OVER SOUTHEAST MONTANA.
STRONG SPEED SHEAR ALOFT MAY LIMIT A WIDE SPREAD OUTBREAK THIS
EVENING BUT A FEW ISOLATED STORMS WITH LARGE HAIL IS POSSIBLE. ALL
MODELS AND WPC CONTINUE TO FORECAST HIGH QPF VALUES OVER THE OUR
AREA TONIGHT THROUGH SATURDAY WITH AN INCH OF QPF FROM LIVINGSTON
TO BROADUS. FLASH FLOODING IS STILL POSSIBLE OVER LAST YEARS BURN
SCARS WITH THESE KIND OF QPF AMOUNTS. IF CONVECTION CELLS BEGIN
TRAINING...THEN FLASH FLOODING WILL LIKELY TAKE PLACE AS RADAR IS
CURRENTLY SHOWING OVER NORTHERN WYOMING. FLASH FLOOD WATCH THROUGH
TONIGHT LOOKS TO BE ON TRACK AND WILL LEAVE IN PLACE.
SATURDAY THROUGH SUNDAY NIGHT...WET WEATHER WILL CONTINUE ACROSS
THE ENTIRE FORECAST AREA DURING THIS TIME PERIOD AS THE UPPER
TROUGH MOVES SLOWLY EASTWARD. HAVE INCREASED POPS WITH MOIST LOW
LEVEL UPSLOPE FLOW CONTINUING AND STRONG FORCING WITH THE UPPER
TROUGH. WPC 1 TO 3 DAY QPF FORECAST HAS AROUND 2 INCHES OF
PRECIPITATION ACROSS MOST OF SOUTH CENTRAL AND SOUTHEAST MONTANA.
THERE ARE SOME MODEL DISCREPANCIES SHOWING UP ON PLACEMENT AND
TIMING OF UPPER LEVEL LIFT AND WILL HOLD OFF ON EXTENDING CURRENT
FLASH FLOOD WATCH. THE UPPER TROUGH WILL BRING DECREASING HEIGHTS
AND AFTERNOON TEMPERATURES WILL FALL TO SLIGHTLY BELOW SEASONAL
NORMAL HIGHS. AFTERNOON READINGS WILL REMAIN IN THE LOW TO MID
60S. RICHMOND
.LONG TERM...VALID FOR MON...TUE...WED...THU...FRI...
STORM SYSTEM CURRENTLY IMPACTING THE REGION WILL BE SLOW TO MOVE
EAST INTO EARLY NEXT WEEK. STILL SOME UNCERTAINTLY WHERE THE MAIN
UPPER LOW WILL CUT OFF INTO THE PLAINS. THE TREND HAS BEEN FURTHER
WEST INTO THE DAKOTAS...KEEPING MUCH OF THE AREA WET EVEN INTO
MONDAY WITH WRAP AROUND MOISTURE. HAVE THEREFORE INCREASED PRECIP
CHANCES MOST AREAS. EVEN LINGERING RAIN CHANCES INTO EASTERN MT
ON TUESDAY. WEAK RIDGING LATE TUESDAY INTO TUESDAY NIGHT WILL BE
SHORT LIVED WITH NEXT UPPER LOW MOVING INTO THE PACIFIC NORTHWEST.
SOME RETURN FLOW OF LOW LEVEL MOISTURE FROM THE SOUTHEAST AHEAD
OF THIS SYSTEM WILL BE BATTLING WITH A DRY SOUTHWEST UPPER FLOW
AHEAD OF SYSTEM. RIGHT NOW...WILL KEEP ANY RISK OF SHOWERS INTO
THE MOUNTAINS OR ISOLATED AT BEST BUT THIS WILL HAVE TO BE
MONITORED AS THE REGION WILL BE ON THE NORTHERN NOSE OF DRY AIR
FROM WEDNESDAY THROUGH FRIDAY OF NEXT WEEK. AS FOR
TEMPERATURES...NO MAJOR FLUCTUATIONS ANTICIPATED WITH READINGS
FAIRLY CLOSE TO SEASONAL NORMS. FRIEDERS
&&
.AVIATION...
SHOWERS AND A FEW THUNDERSTORMS WILL CONTINUE TO MOVE THROUGH THE
REGION OVERNIGHT...BRINGING OCCASIONAL MVFR CONDITIONS. PATCHY
FOG IS EXPECTED TO DEVELOP AFTER 8Z...ENHANCING THE POTENTIAL FOR
LOCALIZED IFR CONDITIONS. STC
&&
.PRELIMINARY POINT TEMP/POPS...
SAT SUN MON TUE WED THU FRI
-----------------------------------------------------------
BIL 050/065 048/064 048/062 045/071 047/071 049/071 049/076
38/T 77/T 86/W 31/B 13/T 32/T 21/B
LVM 045/064 041/061 040/059 037/066 041/071 040/067 041/071
68/T 87/T 85/W 31/B 14/T 43/T 33/T
HDN 050/067 046/065 047/062 044/071 045/073 049/074 048/078
38/T 77/T 86/W 31/E 13/T 32/T 21/B
MLS 054/070 049/066 049/062 046/068 046/071 050/071 048/075
88/T 77/T 86/W 63/W 23/T 32/T 22/T
4BQ 053/069 046/065 047/060 043/063 044/071 048/071 047/075
48/T 67/T 87/W 53/W 12/T 22/T 21/B
BHK 054/069 048/063 047/060 043/061 043/067 048/067 048/070
98/T 77/T 86/W 53/W 22/T 22/T 22/T
SHR 048/066 044/061 043/057 040/064 040/073 046/072 045/076
37/T 67/T 86/W 42/W 13/T 32/T 22/T
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...FLASH FLOOD WATCH IN EFFECT UNTIL 6 AM MDT SATURDAY FOR ZONES
30-31-36>38-57-58.
WY...NONE.
&&
$$
WEATHER.GOV/BILLINGS
000
FXUS65 KMSO 180248
AFDMSO
Area Forecast Discussion
National Weather Service Missoula MT
848 PM MDT Fri May 17 2013
.UPDATE...Canceled the snow advisory for Lost Trail pass.
&&
.DISCUSSION...The snow level has risen high enough that snow on
the pass is not a concern this evening.
&&
.AVIATION...Rain-showers will be on the increase this evening and
through the night for KGPI and nearby areas. Rain will begin to
decrease in coverage later this evening for aviation sites KBTM,
KSMN, and KMSO. Rain will occasionally reduce visibilities and
ceilings as well as obstruct mountain terrain all across western
Montana and Central Idaho. A few thunderstorms will also be
possible in central Idaho as well as northwest Montana this
evening.
&&
.PREV DISCUSSION... /ISSUED 252 PM MDT Fri May 17 2013/
DISCUSSION...
A complex upper level closed low pressure system is slowly moving
across the Northern Rockies and central Idaho. Significant rainfall
amounts are likely through Saturday afternoon
IMPACTS:
25"-.50" through Saturday morning in the valleys of:
West Central & Southwest Montana
East Central Idaho.
25"-.50" through Saturday afternoon in the valleys of:
Northwest Montana (locally higher amounts)
50"-1.0" through Saturday afternoon in the mountains of:
Northwest Montana including Glacier NP.
(locally 1.5" in the highest elevations of Glacier NP.)
Rainfall will be greatest in Glacier NP as the upper low basically
stalls. This will be conducive for a good period of steady rain
through Saturday morning or early afternoon.
The mid & upper level closed low finally moves into Canada midday
leaving behind showery conditions through the afternoon hours in
most of the Northern Rockies. Showery conditions with no major
impacts are expected Sunday in between upper closed lows.
The next closed low dives down from British Columbia along the
Eastern Pacific. Models have slowed this down a bit. However the
potential still exists for a warm and moist southwest flow will be
ushered into the Northern Rockies. This combined with increasing
instability will produce an increasing confidence for thunderstorms
Tuesday afternoon. Strength of thunderstorm are somewhat uncertain.
Confidence remains high for the closed low to impact the Pacific
Northwest in the middle of next week, and confidence is increasing
that Wednesday northwest Montana will be a focal point for
precipitation. Northerly flow on the west side of this system will
bring in very cold air from Canada, while southerly flow will keep
warmer air and rain on the east side of the system. The most
uncertain part of the forecast is where the boundary between the
warm and cold air will line up, which will be a focal point for
precipitation. The most likely scenario for Wednesday with the
current forecast data is for snow in far northwestern Montana and
rain in Glacier National Park. The main concern with this system
is the potential for streams and small river flooding, though
travel over some mountain passes may also be difficult.
Beyond Wednesday, confidence if the forecast drops off quickly.
There is a lot of uncertainty with how it will evolve and interact
with a jet streak moving south of the low pressure center. Some
solutions rapidly move the system out while others cause the low
to split into two spiraling lows that could linger and cause
repeated precipitation events.
AVIATION...Rain-showers will be on the increase this evening and
through the night for KGPI and nearby areas. Rain will begin to
decrease in coverage later this evening for aviation sites KBTM,
KSMN, and KMSO. Rain will occasionally reduce visibilities and
ceilings as well as obstruct mountain terrain all across western
Montana and Central Idaho. A few thunderstorms will also be
possible in central Idaho as well as northwest Montana this
evening.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&
$$
Follow us on Facebook and Twitter!
https://www.facebook.com/US.NationalWeatherService.Missoula.gov
https://www.twitter.com/NWSMissoula
000
FXUS65 KGGW 180246
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
846 PM MDT FRI MAY 17 2013
.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH SUNDAY...
UPDATE...INCREASED POPS SUBSTANTIALLY WHERE A FAIRLY STEADY BAND
OF RAIN SHOWERS EXISTS ACROSS MUCH OF PHILLIPS COUNTY EXTENDING SOUTHEAST
THROUGH PETROLEUM AND GARFIELD COUNTY. THIS BAND THEN EXTENDS EASTWARD
THROUGH PRAIRIE COUNTY AND WIBAUX COUNTY AS WELL. EXPECTING THE
SHOWER ACTIVITY TO SPREAD INTO SOUTHERN VALLEY...MCCONE...AND
DAWSON COUNTIES OVER THE NEXT FEW HOURS. MODELS CONTINUE TO SHOW
THE HEAVIEST RAINFALL ACCUMULATIONS ACROSS SOUTHEASTERN PORTIONS
OF THE CWA THROUGH TONIGHT AND SO AM STICKING WITH HIGHER QPF
THERE FOR NOW. SOME OF THE NORTHEASTERN ZONES MAY SEE A BETTER
CHANCE FOR RAIN TOWARD MORNING AND DURING THE DAY ON SATURDAY. WILL
TAKE A LOOK AT THE LATEST 00Z GUIDANCE AND MAKE ANY NECESSARY
CHANGES WITH THE MORNING PACKAGE. IT DOES APPEAR THAT RAIN CHANCES
WILL CONTINUE FOR NORTHEAST MONTANA THROUGH THE WEEKEND AS A
SURFACE LOW HANGS AROUND OVER THE DAKOTAS AND AS PULSES OF
SHORTWAVE ENERGY PROPAGATE THROUGH SOUTHWEST FLOW ALOFT. MALIAWCO
PREVIOUS SHORT TERM DISCUSSION...
THE UPPER LEVEL FLOW SPLITS AS THE POLAR JET CROSSES OVER THE
WESTERN COAST WITH THE SOUTHERN BRANCH DIGGING OUT A TROUGH OVER
THE FOUR CORNERS AREA AND THE NORTHERN BRANCH PRODUCING A RIDGE
OVER WESTERN CANADA. FOR THE NEXT FEW DAYS...MONTANA WILL RECEIVE
SOME UNSETTLED WEATHER WITH PIECES OF MID LEVEL ENERGY MOVING UP
FROM THE SOUTHWEST TROUGH. A SURFACE LOW ALSO SETS UP OVER THE
WESTERN DAKOTAS WHICH WILL SERVE TO BRING MOISTURE INTO THE AREA
FROM THE EAST AND SOUTHEAST. Q-VECTOR CONVERGENCES SHOWS ALMOST
CONTINUOUS WEAK TO MODERATE DYNAMIC FORCING THROUGH MONDAY
AFTERNOON. FORECAST SOUNDINGS ALSO SHOW AN EXTENDED PERIOD OF
SATURATION...INDICATIVE OF A RAIN EVENT WITH AROUND AN INCH TO 2
INCHES OF TOTAL ACCUMULATION OVER THE NEXT FEW DAYS.
FORECAST SOUNDINGS ALSO HAVE SOME MODEST AMOUNT OF INSTABILITY IN
THEM...BUT WITH LITTLE CAP AND A HIGH PRECIPITABLE WATER CONTENT...THUS
EXPECT RAIN SHOWERS TO BE THE MAIN FEATURE WITH A FEW LOW-TOPPED
THUNDER SHOWERS AT TIMES. MARTIN
.LONG TERM...SUNDAY NIGHT THROUGH FRIDAY...
THE FORECAST MODELS ARE IN REASONABLE AGREEMENT ON THE OVERALL
PATTERN...BUT CONTINUE TO STRUGGLE IN THE ALL IMPORTANT FINER
DETAILS. NORTHEAST MONTANA WILL REMAIN UNDER THE INFLUENCE OF A
WET CUT OFF UPPER LOW THROUGH TUESDAY. UPPER RIDGING LOOKS TO
BUILD IN BRIEFLY BY MIDWEEK POSSIBLY BRINGING A SHORT LIVED DRYING
TREND...WITH ANOTHER UPPER LOW PUSHING IN FROM THE WEST FOR LATE
IN THE WEEK FOR A RETURN TO MORE UNSETTLED CONDITIONS. OVERALL NO
SIGNIFICANT COOL DOWNS OR WARM UPS ARE EXPECTED...AS TEMPS LARGELY
HANG NEAR SEASONAL NORMALS. ONLY TWEAK TO THE GOING FORECAST WAS
TO TREND UP POPS FOR SUNDAY NIGHT AND MONDAY THANKS TO THE LINGERING
UPPER LOW. OTHERWISE THE GOING FORECAST STANDS. GILCHRIST
PREVIOUS
LONG TERM DISCUSSION...MONDAY THROUGH WEDNESDAY...NORTHEAST
MONTANA WILL REMAIN IN A VERY UNSETTLED PATTERN. A SURFACE LOW
PRESSURE SYSTEM WILL TRACK NORTHEASTWARD FROM SOUTH AND EAST OF
OUR FORECAST AREA TOWARDS THE GREAT LAKES REGION. THIS LOW WILL
BECOME VERTICALLY STACKED AS AN UPPER LEVEL TROUGH ACROSS THE
WESTERN U.S. CLOSES OFF AS IT ALSO LIFTS NORTH AND EASTWARD. THIS
SYSTEM WILL BE ASSOCIATED WITH AN ABUNDANCE OF MOISTURE...AND SO
KEPT POPS IN THE LIKELY RANGE FOR MONDAY...GRADUALLY TAPERING THEM
DOWN TO THE CHANCE AND SLIGHT CHANCE RANGE TOWARDS THE MIDDLE OF
THE WEEK AS THE LOW PRESSURE GRADUALLY LETS GO OF ITS INFLUENCE ON
THE CWA. THE 00Z ECMWF IS A BIT SLOWER WITH THE GFS A BIT MORE
PROGRESSIVE WITH THE EXIT TIME OF THIS SYSTEM AND SO OVERALL
CONFIDENCE IS A BIT LOWER TOWARDS THE MIDDLE OF THE WEEK.
NEVERTHELESS...THIS WILL PROVIDE A GOOD OPPORTUNITY FOR STEADY
RAIN SHOWER ACTIVITY AS WELL AS A FEW THUNDERSTORMS THROUGH THE
PERIOD. WILL KEEP TEMPERATURES IN A GRADUAL MODERATING TREND
TOWARDS THE MIDDLE PORTION OF THE WEEK AS THE UPPER LEVEL TROUGH
EVENTUALLY BECOMES REPLACED BY A VERY SMALL SHORTWAVE RIDGE THAT
ATTEMPTS TO BUILD IN DURING THE MIDDLE OF THE WEEK.
WEDNESDAY NIGHT AND BEYOND...ANOTHER UPPER LEVEL TROUGH IS
EXPECTED TO SWING IN FROM THE PACIFIC NORTHWEST AS IT CLOSES
OFF...WHICH WILL BRING ANOTHER ROUND OF PRECIPITATION CHANCES.
THEREFORE KEPT MENTION OF SHOWERS IN THE GRIDS. KEPT TEMPERATURES
FAIRLY STEADY WITH 850MB TEMPERATURES NOT EXHIBITING MUCH CHANGE
TOWARDS THE SECOND HALF OF THE WEEK ACROSS THE FORECAST AREA.
LOOKING AT FAIRLY SEASONABLE READINGS OVERALL BASED ON CURRENT
GUIDANCE. MALIAWCO
&&
.AVIATION...
VFR. AREAS OF SHOWERS WILL CONTINUE TO MOVE THROUGH NORTHEAST
MONTANA OVERNIGHT. IT LOOKS LIKE THE HEAVIEST SHOWERS WILL STAY
WELL TO OUR SOUTH AND EAST SO VFR CONDITIONS SHOULD PREVAIL.
ADDITIONAL SHOWERS ARE EXPECTED TO REDEVELOP OVER EASTERN MONTANA
SATURDAY POSSIBLY BRINGING SCATTERED MVFR CONDITIONS. JAMBA
&&
.HYDROLOGY...
THE NEXT FEW DAYS WILL BE RATHER WET AS AN UPPER-LEVEL TROUGH
AFFECTS THE AREA. SEVERAL DISTURBANCES ASSOCIATED WITH THIS TROUGH
WILL PASS THROUGH WHICH WILL KEEP CHANCES FOR RAIN WITH SOME
THUNDERSTORMS THROUGH EARLY NEXT WEEK. MODEL GUIDANCE DEPICTS HIGH
AMOUNTS OF MOISTURE WITH THIS SYSTEM. AT THIS POINT THE
ENVIRONMENT LOOKS FAVORABLE FOR SLOW- MOVING STORMS WITH HIGHER
PRECIPITATION IN LOCALIZED AREAS.
MOST OF THE BASINS IN NORTHEAST MONTANA WILL BE ABLE TO ACCOMMODATE
THIS AMOUNT OF MOISTURE... AT LEAST EARLY ON IN THE EVENT. THERE IS
SOME CONCERN FOR RAPIDLY RISING STREAMS AND LOCALIZED URBAN
FLOODING AS THE EVENT PERSISTS. SOME FLOODING MAY BECOME AN
ISSUE... ESPECIALLY FOR THE EASTERN AND SOUTHERN COUNTIES WHERE
THE POTENTIAL FOR STRONGER THUNDERSTORMS IS HIGHER.
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
WEATHER.GOV/GLASGOW
|
