000
FXUS65 KTFX 200035
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
635 PM MDT Wed Jun 19 2013
.UPDATE...Strong thunderstorms continue to move across central
Montana but a surface front pushing through southwest Montana is
bringing stable air into the region. Strong and gusty winds have
been reported behind the front and have issued a high wind warning
for Norris Hill in Madison County. As the front continues to push
through the state the strongest storms will move out of my
forecast area. Additional updates are anticipated through the
evening. mpj
&&
.AVIATION...
Updated 2350Z.
Strong to severe thunderstorms will continue to move through
central and north central Montana this evening. A strong surface
cold front has already pushed through portions of southwest
Montana and will continue to move east overnight. Behind the front
a more stable airmass with gusty west winds will move into the
forecast area. VFR conditions should prevail through the period
except for local IFR/MVFR conditions in and around the strongest
storms. Mountain obscurations are expected as well. mpj
&&
.PREV DISCUSSION...
/ISSUED 305 PM MDT Wed Jun 19 2013/
Rest of this afternoon through tonight...A fairly vigorous upper
level low centered over the inland Pacific NW this afternoon will
track slowly east into the Northern Rockies tonight, producing
favorable conditions for severe thunderstorm development across much
of the forecast area late this afternoon through this evening.
Diffluent southerly flow ahead of the upper low and an upper level
jet rounding the base of the trough will support large scale lift
while cooling in the mid levels will produce moderate instability.
Thunderstorms have already initiated over the higher terrain in
Beaverhead County as well as the Absorka range in south central MT
with latest visible satellite imagery also indicating convective
cloud development over the Little Belts. Expect this activity to
increase and coverage while tracking north this afternoon with storm
intensification/organization occurring late this afternoon and
evening as it progresses north into the relatively rich moisture
environment over the north central MT plains. Large hail and strong
gusty winds will be the main threat as storms organize late this
afternoon with a transition to more linear organization as the
storms continue northward toward the Canadian border late tonight.
Low level helicity fields would marginally support an isolated
tornado threat if cells can interact with a weak boundary across
north central MT. Threat for severe storms will diminish from south
to north later this evening with rain and high elevation snow
showers continuing through the night in the Glacier Park area where
snow levels will fall to around 7000 feet late tonight as the cold
pool aloft associated with the upper low moves in from the west.
Hoenisch
Winds will likely approach high wind criteria along the Rocky
Mountain Front on Thursday, but am not anticipating a need for
high wind highlights at this time. The Pacific low pressure system
will linger through the day on Friday, keeping a chance of showers
and (likely weak) afternoon/evening thunderstorms over the area,
as temperatures remain about 10 degrees cooler than normal.
Coulston
Friday night through Wednesday...An upper low over the Pacific
Northwest early Friday evening is forecast to weaken as it moves
over the forecast area on Saturday. Models are fairly wet over
southwest and north central Montana on Saturday so have increased
the chances of precipitation especially over north central
Montana. The remnants of the upper low move out by late Saturday
night and by early Sunday morning it appears the only threat for
precipitation will be over north central Montana and possibly the
mountains of the Rocky Mountain Front. On Sunday an upper ridge
will move through the forecast area and expect a mostly dry
period but then southwest flow aloft returns next week. Models
differ on shortwave details and associated precipitation
patterns. Due to these inconsistencies will go with generally a
chance of showers/thunderstorms over the mountains of the Rocky
Mountain Front with a slight chance of showers/thunderstorms
elsewhere. Cool air associated with the upper low will result in
highs on Saturday of only 55 to 65 except over north central
Montana where highs will be closer to 70. Thereafter expect
gradually warming temperatures. Blank
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 50 67 43 65 / 60 20 20 30
CTB 49 63 41 64 / 90 20 20 30
HLN 50 65 43 67 / 50 30 20 30
BZN 45 68 39 68 / 30 30 20 30
WEY 34 60 31 63 / 20 20 10 10
DLN 42 62 37 66 / 50 30 20 20
HVR 56 72 47 70 / 100 20 20 40
LWT 48 68 42 65 / 80 20 30 40
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
SEVERE THUNDERSTORM WATCH until 10 PM MDT this evening Blaine...
Broadwater...Cascade...Central and Southern Lewis and Clark...
Chouteau...Eastern Glacier...Eastern Pondera...Eastern Teton...
Fergus...Hill...Jefferson...Judith Basin...Liberty...Meagher...
Northern Rocky Mountain Front...Southern Rocky Mountain Front...
Toole.
FLASH FLOOD WATCH until Midnight MDT tonight Blaine...Cascade...
Chouteau...Eastern Glacier...Eastern Pondera...Eastern Teton...
Fergus...Hill...Judith Basin...Liberty...Northern Rocky Mountain
Front...Southern Rocky Mountain Front...Toole.
HIGH WIND WARNING until 11 PM MDT this evening For Route 287
over Norris Hill in Madison County.
&&
$$
weather.gov/greatfalls
000
FXUS65 KTFX 192105
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
305 PM MDT Wed Jun 19 2013
...SEVERE THUNDERSTORMS LIKELY THIS AFTERNOON AND EVENING...
.DISCUSSION...
Rest of this afternoon through tonight...A fairly vigorous upper
level low centered over the inland Pacific NW this afternoon will
track slowly east into the Northern Rockies tonight, producing
favorable conditions for severe thunderstorm development across much
of the forecast area late this afternoon through this evening.
Diffluent southerly flow ahead of the upper low and an upper level
jet rounding the base of the trough will support large scale lift
while cooling in the mid levels will produce moderate instability.
Thunderstorms have already initiated over the higher terrain in
Beaverhead County as well as the Absorka range in south central MT
with latest visible satellite imagery also indicating convective
cloud development over the Little Belts. Expect this activity to
increase and coverage while tracking north this afternoon with storm
intensification/organization occurring late this afternoon and
evening as it progresses north into the relatively rich moisture
environment over the north central MT plains. Large hail and strong
gusty winds will be the main threat as storms organize late this
afternoon with a transition to more linear organization as the
storms continue northward toward the Canadian border late tonight.
Low level helicity fields would marginally support an isolated
tornado threat if cells can interact with a weak boundary across
north central MT. Threat for severe storms will diminish from south
to north later this evening with rain and high elevation snow
showers continuing through the night in the Glacier Park area where
snow levels will fall to around 7000 feet late tonight as the cold
pool aloft associated with the upper low moves in from the west.
Hoenisch
Winds will likely approach high wind criteria along the Rocky
Mountain Front on Thursday, but am not anticipating a need for
high wind highlights at this time. The Pacific low pressure system
will linger through the day on Friday, keeping a chance of showers
and (likely weak) afternoon/evening thunderstorms over the area,
as temperatures remain about 10 degrees cooler than normal.
Coulston
Friday night through Wednesday...An upper low over the Pacific
Northwest early Friday evening is forecast to weaken as it moves
over the forecast area on Saturday. Models are fairly wet over
southwest and north central Montana on Saturday so have increased
the chances of precipitation especially over north central
Montana. The remnants of the upper low move out by late Saturday
night and by early Sunday morning it appears the only threat for
precipitation will be over north central Montana and possibly the
mountains of the Rocky Mountain Front. On Sunday an upper ridge
will move through the forecast area and expect a mostly dry
period but then southwest flow aloft returns next week. Models
differ on shortwave details and associated precipitation
patterns. Due to these inconsistencies will go with generally a
chance of showers/thunderstorms over the mountains of the Rocky
Mountain Front with a slight chance of showers/thunderstorms
elsewhere. Cool air associated with the upper low will result in
highs on Saturday of only 55 to 65 except over north central
Montana where highs will be closer to 70. Thereafter expect
gradually warming temperatures. Blank
&&
.AVIATION...
Updated 1755Z.
There strong possibility for severe thunderstorms with hail in
excess of one inch in diameter and wind gusts in excess of 50 knots
over Central and North Central Montana...especially in the vicinity
of KHVR...LWT...and to a lesser degree KGTF. Also some of the
thunderstorms will have brief heavy rain with IFR ceilings and
visibilities. Expect thunderstorms to develop over southwest Montana
by mid-afternoon then intensify as they move over the plains. Suk
&&
.HYDROLOGY...
Showers and thunderstorms are expected to develop once again this
afternoon over the Rocky Mountain Front and the adjacent plains
along a surface cold front. These showers and thunderstorms are
then expected to spread east across the plains of north central
and central Montana later this afternoon and continue into this
evening. Forecast models are predicting significant rainfall with
these showers, which is expected to occur in rapid bursts with the
thunderstorms. Some localized flash flooding occurred with storms
along the Rocky Mountain Front Tuesday evening. However, the
greater area of concern is across eastern portions of north
central and central Montana that still have moist soil that would
not be able to absorb much rapid rainfall. Forecast models also
indicate that this area will receive the greatest amount of
rainfall. Taking these factors into consideration, have decided to
issue a Flash Flood Watch from noon MDT today until midnight MDT
tonight for all of north central and central Montana. The greatest
threat for flash flooding for the Rocky Mountain Front and
adjacent plains will be this afternoon, while the greatest threat
in the east will likely be after 5 pm MDT.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 50 67 43 65 / 60 20 20 30
CTB 49 63 41 64 / 90 20 20 30
HLN 50 65 43 67 / 50 30 20 30
BZN 45 68 39 68 / 30 30 20 30
WEY 34 60 31 63 / 20 20 10 10
DLN 42 62 37 66 / 50 30 20 20
HVR 56 72 47 70 / 100 20 20 40
LWT 48 68 42 65 / 80 20 30 40
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH until Midnight MDT tonight Blaine...Cascade...
Chouteau...Eastern Glacier...Eastern Pondera...Eastern Teton...
Fergus...Hill...Judith Basin...Liberty...Northern Rocky Mountain
Front...Southern Rocky Mountain Front...Toole.
SEVERE THUNDERSTORM WATCH until 10 PM MDT this evening Blaine...
Broadwater...Cascade...Central and Southern Lewis and Clark...
Chouteau...Eastern Glacier...Eastern Pondera...Eastern Teton...
Fergus...Hill...Jefferson...Judith Basin...Liberty...Meagher...
Northern Rocky Mountain Front...Southern Rocky Mountain Front...
Toole.
&&
$$
SHORT TERM...
LONG TERM...
AVIATION...
weather.gov/greatfalls
000
FXUS65 KTFX 191754
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1155 AM MDT Wed Jun 19 2013
...UPDATE TO AVIATION...
...STRONG TO POSSIBLY SEVERE THUNDERSTORMS THIS AFTERNOON INTO
THIS EVENING...
.UPDATE...
Satellite imagery this morning shows a fairly vigorous upper level
low centered over eastern OR, poised to track east into the
Northern Rockies tonight. As the upper low tracks east today, flow
aloft will increase from the south and southeast with surface low
development occurring over central MT late this afternoon and
evening. SE flow in the low levels will hold relatively high
dewpoint airmass at the surface over north central MT which will
lead to moderate instability late this afternoon and evening. only
question remaining with respect to Thunderstorm strength is the
impact of cloud cloud-cover currently over the central and western
MT. Latest satellite trends do show some of this cloud field
beginning to break up with with lesser cloud-cover upstream in S to
SE flow aloft which should allow for the necessary surface heating
for moderate instability to be realized. Expect initial storms to
develop after noon over the higher terrain of western and SW MT
with these storms moving north and intensifying/organizing late
this afternoon and evening as they encounter richer low level
moisture and more favorable shear. Large hail and damaging winds
still appear to be the main threat with storms this
afternoon/evening and cannot rule out a small (5%) threat for
Tornadoes as weak low level helicity values look to briefly reach
marginal levels across portions of north central MT. Current
gridded forecast covers the situation well with only minor updates
required this morning. Hoenisch
&&
.AVIATION...
Updated 1755Z.
There strong possibility for severe thunderstorms with hail in
excess of one inch in diameter and wind gusts in excess of 50 knots
over Central and North Central Montana...especially in the vicinity
of KHVR...LWT...and to a lesser degree KGTF. Also some of the
thunderstorms will have brief heavy rain with IFR ceilings and
visibilities. Expect thunderstorms to develop over southwest Montana
by mid-afternoon then intensify as they move over the plains. Suk
&&
.HYDROLOGY...
Showers and thunderstorms are expected to develop once again this
afternoon over the Rocky Mountain Front and the adjacent plains
along a surface cold front. These showers and thunderstorms are
then expected to spread east across the plains of north central
and central Montana later this afternoon and continue into this
evening. Forecast models are predicting significant rainfall with
these showers, which is expected to occur in rapid bursts with the
thunderstorms. Some localized flash flooding occurred with storms
along the Rocky Mountain Front Tuesday evening. However, the
greater area of concern is across eastern portions of north
central and central Montana that still have moist soil that would
not be able to absorb much rapid rainfall. Forecast models also
indicate that this area will receive the greatest amount of
rainfall. Taking these factors into consideration, have decided to
issue a Flash Flood Watch from noon MDT today until midnight MDT
tonight for all of north central and central Montana. The greatest
threat for flash flooding for the Rocky Mountain Front and
adjacent plains will be this afternoon, while the greatest threat
in the east will likely be after 5 pm MDT.
&&
.PREV DISCUSSION...
/ISSUED 555 AM MDT Wed Jun 19 2013/
Today through Friday...Thunderstorms from overnight have exited
the area, but another round of potentially severe weather is on
tap for today. The Pacific low pressure system that brought
thunderstorms to the western portion of the forecast area
yesterday will slowly move into the Pacific Northwest today. The
moist, unstable, and diffluent southerly flow ahead of the system
will combine with a strong embedded disturbance and the associated
cold front over the area for more widespread thunderstorm
development than yesterday. Therefore, the Storm Prediction Center
has all of north central/central Montana under a Slight Risk for
severe thunderstorms today. While some storms over the western
plains of north central/central Montana may see marginally severe
thunderstorms (wind gusts around 60 mph, hail around 1 inch in
diameter), the greater focus will be on the eastern plains.
Surface winds there will be breezy and out of the east ahead of
the cold front, which will advect moist air (dewpoints in the
upper 50s to lower 60s) into the area and enhance the instability.
The surface winds will also combine with the stronger winds aloft
to provide strong wind shear (with regard to both speed and
direction) to that area as well. The enhanced instability and
shear will focus the potential for significantly strong
thunderstorms (hail possibly 2+ inches in diameter, wind gusts in
excess of 70 mph) on the eastern TFX plains. Wind shear may even
be strong enough to possibly generate an isolated tornado.
However, all of these ingredients seem to come together later this
afternoon, which means that thunderstorm development there may not
occur until after 4 or 5 pm MDT, while storms farther west will
develop after 1 pm MDT. Forecast models are also indicating that
these storms may produce heavy rainfall, so have issued a Flash
Flood Watch for the area as well (please see Hydrology section for
details). While storms will generate over the higher terrain of
southwest Montana, the potential for severe storms there is low.
Overall, storms will exit the area to the east with the passage of
the cold front this evening. Westerly downslope winds will help
limit overnight precipitation to the western mountains. A much
cooler airmass will also move into the area, possibly bringing
light measurable snow to the mountain peaks. Winds will likely
approach high wind criteria along the Rocky Mountain Front on
Thursday, but am not anticipating a need for high wind highlights
at this time. The Pacific low pressure system will linger through
the day on Friday, keeping a chance of showers and (likely weak)
afternoon/evening thunderstorms over the area, as temperatures
remain about 10 degrees cooler than normal. Coulston
Friday night through Wednesday...An upper low over the Pacific
Northwest early Friday evening is forecast to weaken as it moves
over the forecast area on Saturday. Models are fairly wet over
southwest and north central Montana on Saturday so have increased
the chances of precipitation especially over north central
Montana. The remnants of the upper low move out by late Saturday
night and by early Sunday morning it appears the only threat for
precipitation will be over north central Montana and possibly the
mountains of the Rocky Mountain Front. On Sunday an upper ridge
will move through the forecast area and expect a mostly dry
period but then southwest flow aloft returns next week. Models
differ on shortwave details and associated precipitation
patterns. Due to these inconsistencies will go with generally a
chance of showers/thunderstorms over the mountains of the Rocky
Mountain Front with a slight chance of showers/thunderstorms
elsewhere. Cool air associated with the upper low will result in
highs on Saturday of only 55 to 65 except over north central
Montana where highs will be closer to 70. Thereafter expect
gradually warming temperatures. Blank
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 76 47 67 43 / 80 40 20 20
CTB 74 45 63 41 / 90 70 20 20
HLN 75 46 65 43 / 70 40 30 20
BZN 81 42 68 39 / 40 30 30 20
WEY 69 32 60 31 / 30 30 20 10
DLN 72 39 62 37 / 50 50 30 20
HVR 88 52 72 47 / 60 100 20 20
LWT 83 45 68 42 / 50 80 20 30
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH through this evening Blaine...Cascade...
Chouteau...Eastern Glacier...Eastern Pondera...Eastern Teton...
Fergus...Hill...Judith Basin...Liberty...Northern Rocky Mountain
Front...Southern Rocky Mountain Front...Toole.
&&
$$
weather.gov/greatfalls
000
FXUS65 KTFX 191701
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1101 AM MDT Wed Jun 19 2013
...STRONG TO POSSIBLY SEVERE THUNDERSTORMS THIS AFTERNOON INTO
THIS EVENING...
.UPDATE...
Satellite imagery this morning shows a fairly vigorous upper level
low centered over eastern OR, poised to track east into the
Northern Rockies tonight. As the upper low tracks east today, flow
aloft will increase from the south and southeast with surface low
development occurring over central MT late this afternoon and
evening. SE flow in the low levels will hold relatively high
dewpoint airmass at the surface over north central MT which will
lead to moderate instability late this afternoon and evening. only
question remaining with respect to Thunderstorm strength is the
impact of cloud cloud-cover currently over the central and western
MT. Latest satellite trends do show some of this cloud field
begining to break up with with lesser cloud-cover upstream in S to
SE flow aloft which should allow for the necessary surface heating
for moderate instability to be realized. Expect initial storms to
develop after noon over the higher terrain of western and SW MT
with these storms moving north and intensifying/organizing late
this afternoon and evening as they encounter richer low level
moisture and more favorable shear. Large hail and damaging winds
still appear to be the main threat with storms this
afternoon/evening and cannot rule out a small (5%) threat for
Tornadoes as weak low level helicity values look to briefly reach
marginal levels across portions of north central MT. Current
gridded forecast covers the situation well with only minor updates
required this morning. Hoenisch
&&
.AVIATION...
Updated 1155Z.
The main message today will be the possibility for severe
thunderstorms with hail in excess of one inch in diameter and wind
gusts in excess of 50 knots. Also some of the thunderstorms will
have brief heavy rain with IFR ceilings and visibilities. Expect
thunderstorms to develop over southwest Montana by mid-afternoon
then intensify as they move over the plains. Feel fairly confident
of the timing mentioned in the tafs for the showers/thunderstorms.
One forecast parameter with little confidence is wind. Confidence is
especially low with forecast wind directions. Actually confidence in
wind directions increases tonight as the cold front moves through
and winds shift to the southwest. Blank
&&
.HYDROLOGY...
Showers and thunderstorms are expected to develop once again this
afternoon over the Rocky Mountain Front and the adjacent plains
along a surface cold front. These showers and thunderstorms are
then expected to spread east across the plains of north central
and central Montana later this afternoon and continue into this
evening. Forecast models are predicting significant rainfall with
these showers, which is expected to occur in rapid bursts with the
thunderstorms. Some localized flash flooding occurred with storms
along the Rocky Mountain Front Tuesday evening. However, the
greater area of concern is across eastern portions of north
central and central Montana that still have moist soil that would
not be able to absorb much rapid rainfall. Forecast models also
indicate that this area will receive the greatest amount of
rainfall. Taking these factors into consideration, have decided to
issue a Flash Flood Watch from noon MDT today until midnight MDT
tonight for all of north central and central Montana. The greatest
threat for flash flooding for the Rocky Mountain Front and
adjacent plains will be this afternoon, while the greatest threat
in the east will likely be after 5 pm MDT.
&&
.PREV DISCUSSION...
/ISSUED 555 AM MDT Wed Jun 19 2013/
Today through Friday...Thunderstorms from overnight have exited
the area, but another round of potentially severe weather is on
tap for today. The Pacific low pressure system that brought
thunderstorms to the western portion of the forecast area
yesterday will slowly move into the Pacific Northwest today. The
moist, unstable, and diffluent southerly flow ahead of the system
will combine with a strong embedded disturbance and the associated
cold front over the area for more widespread thunderstorm
development than yesterday. Therefore, the Storm Prediction Center
has all of north central/central Montana under a Slight Risk for
severe thunderstorms today. While some storms over the western
plains of north central/central Montana may see marginally severe
thunderstorms (wind gusts around 60 mph, hail around 1 inch in
diameter), the greater focus will be on the eastern plains.
Surface winds there will be breezy and out of the east ahead of
the cold front, which will advect moist air (dewpoints in the
upper 50s to lower 60s) into the area and enhance the instability.
The surface winds will also combine with the stronger winds aloft
to provide strong wind shear (with regard to both speed and
direction) to that area as well. The enhanced instability and
shear will focus the potential for significantly strong
thunderstorms (hail possibly 2+ inches in diameter, wind gusts in
excess of 70 mph) on the eastern TFX plains. Wind shear may even
be strong enough to possibly generate an isolated tornado.
However, all of these ingredients seem to come together later this
afternoon, which means that thunderstorm development there may not
occur until after 4 or 5 pm MDT, while storms farther west will
develop after 1 pm MDT. Forecast models are also indicating that
these storms may produce heavy rainfall, so have issued a Flash
Flood Watch for the area as well (please see Hydrology section for
details). While storms will generate over the higher terrain of
southwest Montana, the potential for severe storms there is low.
Overall, storms will exit the area to the east with the passage of
the cold front this evening. Westerly downslope winds will help
limit overnight precipitation to the western mountains. A much
cooler airmass will also move into the area, possibly bringing
light measurable snow to the mountain peaks. Winds will likely
approach high wind criteria along the Rocky Mountain Front on
Thursday, but am not anticipating a need for high wind highlights
at this time. The Pacific low pressure system will linger through
the day on Friday, keeping a chance of showers and (likely weak)
afternoon/evening thunderstorms over the area, as temperatures
remain about 10 degrees cooler than normal. Coulston
Friday night through Wednesday...An upper low over the Pacific
Northwest early Friday evening is forecast to weaken as it moves
over the forecast area on Saturday. Models are fairly wet over
southwest and north central Montana on Saturday so have increased
the chances of precipitation especially over north central
Montana. The remnants of the upper low move out by late Saturday
night and by early Sunday morning it appears the only threat for
precipitation will be over north central Montana and possibly the
mountains of the Rocky Mountain Front. On Sunday an upper ridge
will move through the forecast area and expect a mostly dry
period but then southwest flow aloft returns next week. Models
differ on shortwave details and associated precipitation
patterns. Due to these inconsistencies will go with generally a
chance of showers/thunderstorms over the mountains of the Rocky
Mountain Front with a slight chance of showers/thunderstorms
elsewhere. Cool air associated with the upper low will result in
highs on Saturday of only 55 to 65 except over north central
Montana where highs will be closer to 70. Thereafter expect
gradually warming temperatures. Blank
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 76 47 67 43 / 80 40 20 20
CTB 74 45 63 41 / 90 70 20 20
HLN 75 46 65 43 / 70 40 30 20
BZN 81 42 68 39 / 40 30 30 20
WEY 69 32 60 31 / 30 30 20 10
DLN 72 39 62 37 / 50 50 30 20
HVR 88 52 72 47 / 60 100 20 20
LWT 83 45 68 42 / 50 80 20 30
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH through this evening Blaine...Cascade...
Chouteau...Eastern Glacier...Eastern Pondera...Eastern Teton...
Fergus...Hill...Judith Basin...Liberty...Northern Rocky Mountain
Front...Southern Rocky Mountain Front...Toole.
&&
$$
weather.gov/greatfalls
000
FXUS65 KTFX 191156
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
555 AM MDT Wed Jun 19 2013
UPDATED AVIATION SECTION
...STRONG TO POSSIBLY SEVERE THUNDERSTORMS THIS AFTERNOON INTO
THIS EVENING...
.DISCUSSION...
Today through Friday...Thunderstorms from overnight have exited
the area, but another round of potentially severe weather is on
tap for today. The Pacific low pressure system that brought
thunderstorms to the western portion of the forecast area
yesterday will slowly move into the Pacific Northwest today. The
moist, unstable, and diffluent southerly flow ahead of the system
will combine with a strong embedded disturbance and the associated
cold front over the area for more widespread thunderstorm
development than yesterday. Therefore, the Storm Prediction Center
has all of north central/central Montana under a Slight Risk for
severe thunderstorms today. While some storms over the western
plains of north central/central Montana may see marginally severe
thunderstorms (wind gusts around 60 mph, hail around 1 inch in
diameter), the greater focus will be on the eastern plains.
Surface winds there will be breezy and out of the east ahead of
the cold front, which will advect moist air (dewpoints in the
upper 50s to lower 60s) into the area and enhance the instability.
The surface winds will also combine with the stronger winds aloft
to provide strong wind shear (with regard to both speed and
direction) to that area as well. The enhanced instability and
shear will focus the potential for significantly strong
thunderstorms (hail possibly 2+ inches in diameter, wind gusts in
excess of 70 mph) on the eastern TFX plains. Wind shear may even
be strong enough to possibly generate an isolated tornado.
However, all of these ingredients seem to come together later this
afternoon, which means that thunderstorm development there may not
occur until after 4 or 5 pm MDT, while storms farther west will
develop after 1 pm MDT. Forecast models are also indicating that
these storms may produce heavy rainfall, so have issued a Flash
Flood Watch for the area as well (please see Hydrology section for
details). While storms will generate over the higher terrain of
southwest Montana, the potential for severe storms there is low.
Overall, storms will exit the area to the east with the passage of
the cold front this evening. Westerly downslope winds will help
limit overnight precipitation to the western mountains. A much
cooler airmass will also move into the area, possibly bringing
light measurable snow to the mountain peaks. Winds will likely
approach high wind criteria along the Rocky Mountain Front on
Thursday, but am not anticipating a need for high wind highlights
at this time. The Pacific low pressure system will linger through
the day on Friday, keeping a chance of showers and (likely weak)
afternoon/evening thunderstorms over the area, as temperatures
remain about 10 degrees cooler than normal. Coulston
Friday night through Wednesday...An upper low over the Pacific
Northwest early Friday evening is forecast to weaken as it moves
over the forecast area on Saturday. Models are fairly wet over
southwest and north central Montana on Saturday so have increased
the chances of precipitation especially over north central
Montana. The remnants of the upper low move out by late Saturday
night and by early Sunday morning it appears the only threat for
precipitation will be over north central Montana and possibly the
mountains of the Rocky Mountain Front. On Sunday an upper ridge
will move through the forecast area and expect a mostly dry
period but then southwest flow aloft returns next week. Models
differ on shortwave details and associated precipitation
patterns. Due to these inconsistencies will go with generally a
chance of showers/thunderstorms over the mountains of the Rocky
Mountain Front with a slight chance of showers/thunderstorms
elsewhere. Cool air associated with the upper low will result in
highs on Saturday of only 55 to 65 except over north central
Montana where highs will be closer to 70. Thereafter expect
gradually warming temperatures. Blank
&&
.AVIATION...
Updated 1155Z.
The main message today will be the possibility for severe
thunderstorms with hail in excess of one inch in diameter and wind
gusts in excess of 50 knots. Also some of the thunderstorms will
have brief heavy rain with IFR ceilings and visibilities. Expect
thunderstorms to develop over southwest Montana by mid-afternoon
then intensify as they move over the plains. Feel fairly confident
of the timing mentioned in the tafs for the showers/thunderstorms.
One forecast parameter with little confidence is wind. Confidence is
especially low with forecast wind directions. Actually confidence in
wind directions increases tonight as the cold front moves through
and winds shift to the southwest. Blank
&&
.HYDROLOGY...
Showers and thunderstorms are expected to develop once again this
afternoon over the Rocky Mountain Front and the adjacent plains
along a surface cold front. These showers and thunderstorms are
then expected to spread east across the plains of north central
and central Montana later this afternoon and continue into this
evening. Forecast models are predicting significant rainfall with
these showers, which is expected to occur in rapid bursts with the
thunderstorms. Some localized flash flooding occurred with storms
along the Rocky Mountain Front Tuesday evening. However, the
greater area of concern is across eastern portions of north
central and central Montana that still have moist soil that would
not be able to absorb much rapid rainfall. Forecast models also
indicate that this area will receive the greatest amount of
rainfall. Taking these factors into consideration, have decided to
issue a Flash Flood Watch from noon MDT today until midnight MDT
tonight for all of north central and central Montana. The greatest
threat for flash flooding for the Rocky Mountain Front and
adjacent plains will be this afternoon, while the greatest threat
in the east will likely be after 5 pm MDT.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 76 47 67 43 / 90 40 20 20
CTB 74 45 63 41 / 100 70 20 20
HLN 75 46 65 43 / 70 40 30 20
BZN 81 42 68 39 / 40 30 30 20
WEY 69 32 60 31 / 40 30 20 10
DLN 72 39 62 37 / 60 50 30 20
HVR 88 52 72 47 / 60 100 20 20
LWT 83 45 68 42 / 60 80 20 30
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH from Noon MDT today through this evening
Blaine...Cascade...Chouteau...Eastern Glacier...Eastern
Pondera...Eastern Teton...Fergus...Hill...Judith Basin...
Liberty...Northern Rocky Mountain Front...Southern Rocky
Mountain Front...Toole.
&&
$$
SHORT TERM...COULSTON
LONG TERM...BLANK
AVIATION...mpj
weather.gov/greatfalls
000
FXUS65 KTFX 191048
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
448 AM MDT Wed Jun 19 2013
...Strong to possibly severe thunderstorms today into this
evening...
.DISCUSSION...
Today through Friday...Thunderstorms from overnight have exited
the area, but another round of potentially severe weather is on
tap for today. The Pacific low pressure system that brought
thunderstorms to the western portion of the forecast area
yesterday will slowly move into the Pacific Northwest today. The
moist, unstable, and diffluent southerly flow ahead of the system
will combine with a strong embedded disturbance and the associated
cold front over the area for more widespread thunderstorm
development than yesterday. Therefore, the Storm Prediction Center
has all of north central/central Montana under a Slight Risk for
severe thunderstorms today. While some storms over the western
plains of north central/central Montana may see marginally severe
thunderstorms (wind gusts around 60 mph, hail around 1 inch in
diameter), the greater focus will be on the eastern plains.
Surface winds there will be breezy and out of the east ahead of
the cold front, which will advect moist air (dewpoints in the
upper 50s to lower 60s) into the area and enhance the instability.
The surface winds will also combine with the stronger winds aloft
to provide strong wind shear (with regard to both speed and
direction) to that area as well. The enhanced instability and
shear will focus the potential for significantly strong
thunderstorms (hail possibly 2+ inches in diameter, wind gusts in
excess of 70 mph) on the eastern TFX plains. Wind shear may even
be strong enough to possibly generate an isolated tornado.
However, all of these ingredients seem to come together later this
afternoon, which means that thunderstorm development there may not
occur until after 4 or 5 pm MDT, while storms farther west will
develop after 1 pm MDT. Forecast models are also indicating that
these storms may produce heavy rainfall, so have issued a Flash
Flood Watch for the area as well (please see Hydrology section for
details). While storms will generate over the higher terrain of
southwest Montana, the potential for severe storms there is low.
Overall, storms will exit the area to the east with the passage of
the cold front this evening. Westerly downslope winds will help
limit overnight precipitation to the western mountains. A much
cooler airmass will also move into the area, possibly bringing
light measurable snow to the mountain peaks. Winds will likely
approach high wind criteria along the Rocky Mountain Front on
Thursday, but am not anticipating a need for high wind highlights
at this time. The Pacific low pressure system will linger through
the day on Friday, keeping a chance of showers and (likely weak)
afternoon/evening thunderstorms over the area, as temperatures
remain about 10 degrees cooler than normal. Coulston
Friday night through Wednesday...An upper low over the Pacific
Northwest early Friday evening is forecast to weaken as it moves
over the forecast area on Saturday. Models are fairly wet over
southwest and north central Montana on Saturday so have increased
the chances of precipitation especially over north central
Montana. The remnants of the upper low move out by late Saturday
night and by early Sunday morning it appears the only threat for
precipitation will be over north central Montana and possibly the
mountains of the Rocky Mountain Front. On Sunday an upper ridge
will move through the forecast area and expect a mostly dry
period but then southwest flow aloft returns next week. Models
differ on shortwave details and associated precipitation
patterns. Due to these inconsistencies will go with generally a
chance of showers/thunderstorms over the mountains of the Rocky
Mountain Front with a slight chance of showers/thunderstorms
elsewhere. Cool air associated with the upper low will result in
highs on Saturday of only 55 to 65 except over north central
Montana where highs will be closer to 70. Thereafter expect
gradually warming temperatures. Blank
&&
.AVIATION...
Updated 0450Z.
Widespread showers and thunderstorms will continue to move
through western portions of north central Montana through 10Z.
During this time, areas of MVFR conditions in heavy rain remain
possible along with mountain obscurations. A surface cold front
will push east of the continental divide Wednesday afternoon then
moves into eastern Montana after 03Z. Another round of strong to
severe thunderstorms will develop ahead of the frontal boundary
but clearing skies and calmer weather will move in behind the
front. mpj
&&
.HYDROLOGY...
Showers and thunderstorms are expected to develop once again this
afternoon over the Rocky Mountain Front and the adjacent plains
along a surface cold front. These showers and thunderstorms are
then expected to spread east across the plains of north central
and central Montana later this afternoon and continue into this
evening. Forecast models are predicting significant rainfall with
these showers, which is expected to occur in rapid bursts with the
thunderstorms. Some localized flash flooding occurred with storms
along the Rocky Mountain Front Tuesday evening. However, the
greater area of concern is across eastern portions of north
central and central Montana that still have moist soil that would
not be able to absorb much rapid rainfall. Forecast models also
indicate that this area will receive the greatest amount of
rainfall. Taking these factors into consideration, have decided to
issue a Flash Flood Watch from noon MDT today until midnight MDT
tonight for all of north central and central Montana. The greatest
threat for flash flooding for the Rocky Mountain Front and
adjacent plains will be this afternoon, while the greatest threat
in the east will likely be after 5 pm MDT.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 76 47 67 43 / 90 40 20 20
CTB 74 45 63 41 / 100 70 20 20
HLN 75 46 65 43 / 70 40 30 20
BZN 81 42 68 39 / 40 30 30 20
WEY 69 32 60 31 / 40 30 20 10
DLN 72 39 62 37 / 60 50 30 20
HVR 88 52 72 47 / 60 100 20 20
LWT 83 45 68 42 / 60 80 20 30
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH from Noon MDT today through this evening
Blaine...Cascade...Chouteau...Eastern Glacier...Eastern
Pondera...Eastern Teton...Fergus...Hill...Judith Basin...
Liberty...Northern Rocky Mountain Front...Southern Rocky
Mountain Front...Toole.
&&
$$
SHORT TERM...COULSTON
LONG TERM...BLANK
AVIATION...mpj
weather.gov/greatfalls
000
FXUS65 KTFX 190451
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1050 PM MDT Tue Jun 18 2013
...UPDATE TO AVIATION...
.UPDATE...
A few strong thunderstorms continue to push northward through the
region. The thunderstorm watch will continue a bit longer where it
is currently in effect in case a severe storm develops. The flash
flood warnings will continue a bit longer as well. Expect a few
thunderstorms to continue after midnight. Otherwise current
forecast is on track. Brusda
&&
.AVIATION...
Updated 0450Z.
Widespread showers and thunderstorms will continue to move through
western portions of north central Montana through 10Z. During this
time, areas of MVFR conditions in heavy rain remain possible along
with mountain obscurations. A surface cold front will push east of
the continental divide Wednesday afternoon then moves into eastern
Montana after 03Z. Another round of strong to severe thunderstorms
will develop ahead of the frontal boundary but clearing skies and
calmer weather will move in behind the front. mpj
&&
.HYDROLOGY...
More widespread showers and thunderstorms are possible along the
Rocky Mountain Front and adjacent plains this afternoon and
evening and over most of the plains of North Central/Central
Montana on Wednesday. Some of these storms may produce brief heavy
rainfall. These periods will need to be monitored for possible
areal flood/flash flood highlights. The greater area of concern is
across eastern portions of north central and central Montana for
Wednesday that still have moist soil that would not be able to
absorb much rapid rainfall. If rainfall from storms today are
significant along the Rocky Mountain Front additional rainfall on
Wednesday will increase the flooding threat there as well.
&&
.PREV DISCUSSION...
/ISSUED 555 PM MDT Tue Jun 18 2013/
Today through Thursday...A low pressure system moving over the
Pacific Northwest coast today will bring increased moisture and
instability to Montana. These factors will help generate showers and
thunderstorms over terrain this afternoon. A frontal boundary
associated with this system will also move into Western Montana
today providing a good forcing mechanism for storm development. As a
result the Storm Prediction Center continues to keep Western and
Central Montana under a Slight Risk for severe thunderstorms. Storms
decrease overnight, but another round of potentially severe weather
is expected for Wednesday as the main system continues to move east
across the Northern Rockies. The most unstable conditions will also
shift northeast into Central and Eastern Montana, where the Storm
Prediction Center has a Slight Risk for Wednesday as well. The
potential for the strongest storms will be along and east of a
Havre-to-Stanford line as wind shear and instability are strongest
there. Precipitation from storms may be heavy adding the potential
for flash flooding. The system will lift northeast across the area
later Wednesday night into Thursday keeping high POPs in the
mountains. Westerly down-slope winds will hinder shower/thunderstorm
development Thursday though. Winds strengthen along the Rocky
Mountain Front Thursday making high wind highlights possible.
Temperatures cool Wednesday as the main front moves through the area.
Thursday night through Tuesday...No significant changes made to
the medium range forecast. An unsettled pattern will persist
through Saturday as a closed upper low will remain quasi-
stationary over northwest Montana. Short wave energy will
continue to rotate out from the base of the low and help initiate
shower and thunderstorm development each day. The strength of
these storms will depend on availability of low level moisture
and the strength of the divergent flow aloft. The models also
continue to differ on the upper low`s position which, in turn,
will affect where and how strong thunderstorms will be. Because
of these differences, have continued to broad-brush the pops
through Saturday. By late Saturday, the models move the low to
northeast Montana and lift it out as an upper ridge begins
building over the Pacific Northwest. The ridge breaks down on
Sunday as short wave energy ripples across the area within the
westerly flow aloft. Isolated thunderstorms will remain a
possibility Sunday and Monday. By Tuesday, weak upper ridging
returns though isolated showers will persist over the southwest
mountains. Temperatures will remain below seasonal averages to
start the period due to cloud cover and periodic cold advection
from transient shortwaves. Temperatures should rise above
seasonal averages to start the week.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 54 76 46 67 / 40 80 80 20
CTB 52 73 45 64 / 100 100 90 30
HLN 53 75 46 67 / 50 70 60 30
BZN 48 79 42 69 / 20 50 40 20
WEY 38 70 32 61 / 10 30 20 20
DLN 48 71 39 65 / 20 60 50 20
HVR 59 84 51 73 / 20 80 90 20
LWT 53 80 44 69 / 20 60 80 20
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
weather.gov/greatfalls
000
FXUS65 KTFX 190305
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
905 PM MDT Tue Jun 18 2013
.UPDATE...
A few strong thunderstorms continue to push northward through the
region. The thunderstorm watch will continue a bit longer where it
is currently in effect in case a severe storm develops. The flash
flood warnings will continue a bit longer as well. Expect a few
thunderstorms to continue after midnight. Otherwise current
forecast is on track. Brusda
&&
.AVIATION...
Updated 2355Z.
Widespread thunderstorm activity, mainly west of I-15 and north of
KBTM, will continue into the evening hours. Some storms are
producing large hail and very heavy rain. Less than VFR conditions
can be expected in heavy precipitation. Convective activity
diminishes after 06Z but another round of thunderstorms will develop
Wednesday. mpj
&&
.HYDROLOGY...
More widespread showers and thunderstorms are possible along the
Rocky Mountain Front and adjacent plains this afternoon and
evening and over most of the plains of North Central/Central
Montana on Wednesday. Some of these storms may produce brief heavy
rainfall. These periods will need to be monitored for possible
areal flood/flash flood highlights. The greater area of concern is
across eastern portions of north central and central Montana for
Wednesday that still have moist soil that would not be able to
absorb much rapid rainfall. If rainfall from storms today are
significant along the Rocky Mountain Front additional rainfall on
Wednesday will increase the flooding threat there as well.
&&
.PREV DISCUSSION...
/ISSUED 555 PM MDT Tue Jun 18 2013/
Today through Thursday...A low pressure system moving over the
Pacific Northwest coast today will bring increased moisture and
instability to Montana. These factors will help generate showers and
thunderstorms over terrain this afternoon. A frontal boundary
associated with this system will also move into Western Montana
today providing a good forcing mechanism for storm development. As a
result the Storm Prediction Center continues to keep Western and
Central Montana under a Slight Risk for severe thunderstorms. Storms
decrease overnight, but another round of potentially severe weather
is expected for Wednesday as the main system continues to move east
across the Northern Rockies. The most unstable conditions will also
shift northeast into Central and Eastern Montana, where the Storm
Prediction Center has a Slight Risk for Wednesday as well. The
potential for the strongest storms will be along and east of a
Havre-to-Stanford line as wind shear and instability are strongest
there. Precipitation from storms may be heavy adding the potential
for flash flooding. The system will lift northeast across the area
later Wednesday night into Thursday keeping high POPs in the
mountains. Westerly down-slope winds will hinder shower/thunderstorm
development Thursday though. Winds strengthen along the Rocky
Mountain Front Thursday making high wind highlights possible.
Temperatures cool Wednesday as the main front moves through the area.
Thursday night through Tuesday...No significant changes made to
the medium range forecast. An unsettled pattern will persist
through Saturday as a closed upper low will remain quasi-
stationary over northwest Montana. Short wave energy will
continue to rotate out from the base of the low and help initiate
shower and thunderstorm development each day. The strength of
these storms will depend on availability of low level moisture
and the strength of the divergent flow aloft. The models also
continue to differ on the upper low`s position which, in turn,
will affect where and how strong thunderstorms will be. Because
of these differences, have continued to broad-brush the pops
through Saturday. By late Saturday, the models move the low to
northeast Montana and lift it out as an upper ridge begins
building over the Pacific Northwest. The ridge breaks down on
Sunday as short wave energy ripples across the area within the
westerly flow aloft. Isolated thunderstorms will remain a
possibility Sunday and Monday. By Tuesday, weak upper ridging
returns though isolated showers will persist over the southwest
mountains. Temperatures will remain below seasonal averages to
start the period due to cloud cover and periodic cold advection
from transient shortwaves. Temperatures should rise above
seasonal averages to start the week.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 54 76 46 67 / 40 80 80 20
CTB 52 73 45 64 / 100 100 90 30
HLN 53 75 46 67 / 50 70 60 30
BZN 48 79 42 69 / 20 50 40 20
WEY 38 70 32 61 / 10 30 20 20
DLN 48 71 39 65 / 20 60 50 20
HVR 59 84 51 73 / 20 80 90 20
LWT 53 80 44 69 / 20 60 80 20
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
SEVERE THUNDERSTORM WATCH until 10 PM MDT this evening Eastern
Glacier...Eastern Pondera...Eastern Teton...Liberty...Northern
Rocky Mountain Front...Southern Rocky Mountain Front...Toole.
&&
$$
weather.gov/greatfalls
000
FXUS65 KTFX 190053
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
653 PM MDT Tue Jun 18 2013
.UPDATE...Strong to severe thunderstorms will continue to affect my
northwest zones through the evening hours. Have updated the
forecast to increase pops across this area for the remainder of
tonight. There is some concern that widespread heavy rains in this
area may cause flooding concerns. This potential will continue to
be monitored through the night. mpj
&&
.AVIATION...
Updated 2355Z.
Widespread thunderstorm activity, mainly west of I-15 and north of
KBTM, will continue into the evening hours. Some storms are
producing large hail and very heavy rain. Less than VFR conditions
can be expected in heavy precipitation. Convective activity
diminishes after 06Z but another round of thunderstorms will develop
Wednesday. mpj
&&
.HYDROLOGY...
More widespread showers and thunderstorms are possible along the
Rocky Mountain Front and adjacent plains this afternoon and
evening and over most of the plains of North Central/Central
Montana on Wednesday. Some of these storms may produce brief heavy
rainfall. These periods will need to be monitored for possible
areal flood/flash flood highlights. The greater area of concern is
across eastern portions of north central and central Montana for
Wednesday that still have moist soil that would not be able to
absorb much rapid rainfall. If rainfall from storms today are
significant along the Rocky Mountain Front additional rainfall on
Wednesday will increase the flooding threat there as well.
&&
.PREV DISCUSSION...
/ISSUED 555 PM MDT Tue Jun 18 2013/
Today through Thursday...A low pressure system moving over the
Pacific Northwest coast today will bring increased moisture and
instability to Montana. These factors will help generate showers and
thunderstorms over terrain this afternoon. A frontal boundary
associated with this system will also move into Western Montana
today providing a good forcing mechanism for storm development. As a
result the Storm Prediction Center continues to keep Western and
Central Montana under a Slight Risk for severe thunderstorms. Storms
decrease overnight, but another round of potentially severe weather
is expected for Wednesday as the main system continues to move east
across the Northern Rockies. The most unstable conditions will also
shift northeast into Central and Eastern Montana, where the Storm
Prediction Center has a Slight Risk for Wednesday as well. The
potential for the strongest storms will be along and east of a
Havre-to-Stanford line as wind shear and instability are strongest
there. Precipitation from storms may be heavy adding the potential
for flash flooding. The system will lift northeast across the area
later Wednesday night into Thursday keeping high POPs in the
mountains. Westerly down-slope winds will hinder shower/thunderstorm
development Thursday though. Winds strengthen along the Rocky
Mountain Front Thursday making high wind highlights possible.
Temperatures cool Wednesday as the main front moves through the area.
Thursday night through Tuesday...No significant changes made to
the medium range forecast. An unsettled pattern will persist
through Saturday as a closed upper low will remain quasi-
stationary over northwest Montana. Short wave energy will
continue to rotate out from the base of the low and help initiate
shower and thunderstorm development each day. The strength of
these storms will depend on availability of low level moisture
and the strength of the divergent flow aloft. The models also
continue to differ on the upper low`s position which, in turn,
will affect where and how strong thunderstorms will be. Because
of these differences, have continued to broad-brush the pops
through Saturday. By late Saturday, the models move the low to
northeast Montana and lift it out as an upper ridge begins
building over the Pacific Northwest. The ridge breaks down on
Sunday as short wave energy ripples across the area within the
westerly flow aloft. Isolated thunderstorms will remain a
possibility Sunday and Monday. By Tuesday, weak upper ridging
returns though isolated showers will persist over the southwest
mountains. Temperatures will remain below seasonal averages to
start the period due to cloud cover and periodic cold advection
from transient shortwaves. Temperatures should rise above
seasonal averages to start the week.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 54 76 46 67 / 40 80 80 20
CTB 52 73 45 64 / 100 100 90 30
HLN 53 75 46 67 / 50 70 60 30
BZN 48 79 42 69 / 30 50 40 20
WEY 38 70 32 61 / 20 30 20 20
DLN 48 71 39 65 / 20 60 50 20
HVR 59 84 51 73 / 20 80 90 20
LWT 53 80 44 69 / 20 60 80 20
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
SEVERE THUNDERSTORM WATCH until 10 PM MDT this evening
Broadwater...Cascade...Central and Southern Lewis and Clark...
Chouteau...Eastern Glacier...Eastern Pondera...Eastern Teton...
Hill...Jefferson...Judith Basin...Liberty...Meagher...Northern
Rocky Mountain Front...Southern Rocky Mountain Front...Toole.
&&
$$
weather.gov/greatfalls
000
FXUS65 KTFX 182352
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
555 PM MDT Tue Jun 18 2013
...UPDATE TO AVIATION...
.DISCUSSION...
Today through Thursday...A low pressure system moving over the
Pacific Northwest coast today will bring increased moisture and
instability to Montana. These factors will help generate showers and
thunderstorms over terrain this afternoon. A frontal boundary
associated with this system will also move into Western Montana
today providing a good forcing mechanism for storm development. As a
result the Storm Prediction Center continues to keep Western and
Central Montana under a Slight Risk for severe thunderstorms. Storms
decrease overnight, but another round of potentially severe weather
is expected for Wednesday as the main system continues to move east
across the Northern Rockies. The most unstable conditions will also
shift northeast into Central and Eastern Montana, where the Storm
Prediction Center has a Slight Risk for Wednesday as well. The
potential for the strongest storms will be along and east of a
Havre-to-Stanford line as wind shear and instability are strongest
there. Precipitation from storms may be heavy adding the potential
for flash flooding. The system will lift northeast across the area
later Wednesday night into Thursday keeping high POPs in the
mountains. Westerly down-slope winds will hinder shower/thunderstorm
development Thursday though. Winds strengthen along the Rocky
Mountain Front Thursday making high wind highlights possible.
Temperatures cool Wednesday as the main front moves through the area.
Thursday night through Tuesday...No significant changes made to
the medium range forecast. An unsettled pattern will persist
through Saturday as a closed upper low will remain quasi-
stationary over northwest Montana. Short wave energy will
continue to rotate out from the base of the low and help initiate
shower and thunderstorm development each day. The strength of
these storms will depend on availability of low level moisture
and the strength of the divergent flow aloft. The models also
continue to differ on the upper low`s position which, in turn,
will affect where and how strong thunderstorms will be. Because
of these differences, have continued to broad-brush the pops
through Saturday. By late Saturday, the models move the low to
northeast Montana and lift it out as an upper ridge begins
building over the Pacific Northwest. The ridge breaks down on
Sunday as short wave energy ripples across the area within the
westerly flow aloft. Isolated thunderstorms will remain a
possibility Sunday and Monday. By Tuesday, weak upper ridging
returns though isolated showers will persist over the southwest
mountains. Temperatures will remain below seasonal averages to
start the period due to cloud cover and periodic cold advection
from transient shortwaves. Temperatures should rise above
seasonal averages to start the week.
&&
.AVIATION...
Updated 2355Z.
Widespread thunderstorm activity, mainly west of I-15 and north of
KBTM, will continue into the evening hours. Some storms are
producing large hail and very heavy rain. Less than VFR conditions
can be expected in heavy precipitation. Convective activity
diminishes after 06Z but another round of thunderstorms will develop
Wednesday. mpj
&&
.HYDROLOGY...
More widespread showers and thunderstorms are possible along the
Rocky Mountain Front and adjacent plains this afternoon and
evening and over most of the plains of North Central/Central
Montana on Wednesday. Some of these storms may produce brief heavy
rainfall. These periods will need to be monitored for possible
areal flood/flash flood highlights. The greater area of concern is
across eastern portions of north central and central Montana for
Wednesday that still have moist soil that would not be able to
absorb much rapid rainfall. If rainfall from storms today are
significant along the Rocky Mountain Front additional rainfall on
Wednesday will increase the flooding threat there as well.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 54 76 46 67 / 60 80 80 20
CTB 52 73 45 64 / 70 100 90 30
HLN 53 75 46 67 / 50 70 60 30
BZN 48 79 42 69 / 30 50 40 20
WEY 38 70 32 61 / 20 30 20 20
DLN 48 71 39 65 / 40 60 50 20
HVR 59 84 51 73 / 50 80 90 20
LWT 53 80 44 69 / 40 60 80 20
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
SEVERE THUNDERSTORM WATCH until 10 PM MDT this evening
Broadwater...Cascade...Central and Southern Lewis and Clark...
Chouteau...Eastern Glacier...Eastern Pondera...Eastern Teton...
Hill...Jefferson...Judith Basin...Liberty...Meagher...Northern
Rocky Mountain Front...Southern Rocky Mountain Front...Toole.
&&
$$
weather.gov/greatfalls
000
FXUS65 KTFX 182043
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
243 PM MDT Tue Jun 18 2013
.DISCUSSION...
Today through Thursday...A low pressure system moving over the
Pacific Northwest coast today will bring increased moisture and
instability to Montana. These factors will help generate showers and
thunderstorms over terrain this afternoon. A frontal boundary
associated with this system will also move into Western Montana
today providing a good forcing mechanism for storm development. As a
result the Storm Prediction Center continues to keep Western and
Central Montana under a Slight Risk for severe thunderstorms. Storms
decrease overnight, but another round of potentially severe weather
is expected for Wednesday as the main system continues to move east
across the Northern Rockies. The most unstable conditions will also
shift northeast into Central and Eastern Montana, where the Storm
Prediction Center has a Slight Risk for Wednesday as well. The
potential for the strongest storms will be along and east of a
Havre-to-Stanford line as wind shear and instability are strongest
there. Precipitation from storms may be heavy adding the potential
for flash flooding. The system will lift northeast across the area
later Wednesday night into Thursday keeping high POPs in the
mountains. Westerly down-slope winds will hinder shower/thunderstorm
development Thursday though. Winds strengthen along the Rocky
Mountain Front Thursday making high wind highlights possible.
Temperatures cool Wednesday as the main front moves through the area.
Thursday night through Tuesday...No significant changes made to
the medium range forecast. An unsettled pattern will persist
through Saturday as a closed upper low will remain quasi-
stationary over northwest Montana. Short wave energy will
continue to rotate out from the base of the low and help initiate
shower and thunderstorm development each day. The strength of
these storms will depend on availability of low level moisture
and the strength of the divergent flow aloft. The models also
continue to differ on the upper low`s position which, in turn,
will affect where and how strong thunderstorms will be. Because
of these differences, have continued to broad-brush the pops
through Saturday. By late Saturday, the models move the low to
northeast Montana and lift it out as an upper ridge begins
building over the Pacific Northwest. The ridge breaks down on
Sunday as short wave energy ripples across the area within the
westerly flow aloft. Isolated thunderstorms will remain a
possibility Sunday and Monday. By Tuesday, weak upper ridging
returns though isolated showers will persist over the southwest
mountains. Temperatures will remain below seasonal averages to
start the period due to cloud cover and periodic cold advection
from transient shortwaves. Temperatures should rise above
seasonal averages to start the week.
&&
.AVIATION...
Updated 1725Z.
A trof over the Pacific Northwest will continue to influence the
weather across the area through 18Z Wednesday. Thunderstorms will
initially develop over the mountains early this afternoon and begin
to push into the plains late in the afternoon. The most widespread
thunderstorms activity will be in the KCTB area where a cold front
will approach this evening. Some of the storms cloud contain large
hail and strong wind gusts to 50 knots...mainly north and west of a
KBTM to KGTF to KHVR line. Less than VFR conditions can be expected
with some of the heavier storms. The threat for storms will be lower
in KLWT and KBZN area where lack of lift and/or drier air will limit
thunderstorm coverage. Langlieb
&&
.HYDROLOGY...
More widespread showers and thunderstorms are possible along the
Rocky Mountain Front and adjacent plains this afternoon and
evening and over most of the plains of North Central/Central
Montana on Wednesday. Some of these storms may produce brief heavy
rainfall. These periods will need to be monitored for possible
areal flood/flash flood highlights. The greater area of concern is
across eastern portions of north central and central Montana for
Wednesday that still have moist soil that would not be able to
absorb much rapid rainfall. If rainfall from storms today are
significant along the Rocky Mountain Front additional rainfall on
Wednesday will increase the flooding threat there as well.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 54 76 46 67 / 60 80 80 20
CTB 52 73 45 64 / 70 100 90 30
HLN 53 75 46 67 / 50 70 60 30
BZN 48 79 42 69 / 30 50 40 20
WEY 38 70 32 61 / 20 30 20 20
DLN 48 71 39 65 / 40 60 50 20
HVR 59 84 51 73 / 50 80 90 20
LWT 53 80 44 69 / 40 60 80 20
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
SEVERE THUNDERSTORM WATCH until 10 PM MDT this evening
Broadwater...Cascade...Central and Southern Lewis and Clark...
Chouteau...Eastern Glacier...Eastern Pondera...Eastern Teton...
Hill...Jefferson...Judith Basin...Liberty...Meagher...Northern
Rocky Mountain Front...Southern Rocky Mountain Front...Toole.
&&
$$
weather.gov/greatfalls
000
FXUS65 KTFX 181724
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1125 AM MDT Tue Jun 18 2013
UPDATED AVIATION SECTION
.UPDATE...
Minor updates to the forecast this morning. Adjusted POP a bit
based on current model data. Still expecting convective activity
with best chances developing over terrain this afternoon.
&&
.AVIATION...
Updated 1725Z.
A trof over the Pacific Northwest will continue to influence the
weather across the area through 18Z Wednesday. Thunderstorms will
initially develop over the mountains early this afternoon and begin
to push into the plains late in the afternoon. The most widespread
thunderstorms activity will be in the KCTB area where a cold front
will approach this evening. Some of the storms cloud contain large
hail and strong wind gusts to 50 knots...mainly north and west of a
KBTM to KGTF to KHVR line. Less than VFR conditions can be expected
with some of the heavier storms. The threat for storms will be lower
in KLWT and KBZN area where lack of lift and/or drier air will limit
thunderstorm coverage. Langlieb
&&
.HYDROLOGY...
More widespread showers and thunderstorms are possible along the
Rocky Mountain Front and adjacent plains today and over most of
the plains of north central/central Montana on Wednesday. Some of
these storms may produce brief heavy rainfall. These periods will
need to be monitored for possible areal flood/flash flood
highlights. The greater area of concern is across eastern portions
of north central and central Montana for Wednesday that still
have moist soil that would not be able to absorb much rapid
rainfall. However, if the rainfall from storms today are
significant along the Rocky Mountain Front, the additional rainfall
on Wednesday will increase the flooding threat there as well.
&&
.PREV DISCUSSION...
/ISSUED 555 AM MDT Tue Jun 18 2013/
Today through Thursday...Forecast models continue to indicate that
strong to possibly severe thunderstorms are possible both today
and Wednesday. As the Pacific low pressure system moves onto the
Pacific Northwest coast today, the flow aloft over western and
central Montana will become more moist, unstable, and
southwesterly. Temperatures will also warm to around 10 degrees
above normal. These factors will help generate showers and
thunderstorms over the higher terrain of these areas. The frontal
boundary associated with this system will also move into western
Montana today to provide a good focusing mechanism for storm
development. The flow aloft will also become more diffluent, which
should enhance vertical development of storms. These factors,
along with strong wind shear (both speed and directional) and
significant instability (CAPE values of 1500 to 2500 J/kg), the
Storm Prediction Center (SPC) has put portions of western and
central Montana under a Slight Risk for severe thunderstorms, and
we have subsequently added mention of damaging winds, large hail,
and heavy rainfall for this area. This area is generally northwest
of a Havre-to- Butte line. Thunderstorms will decrease overnight,
but another round of potentially severe weather is expected for
Wednesday as the system continues to move east across the Pacific
Northwest. The most unstable portion of the flow aloft and the
surface frontal boundary will also shift east into central and
eastern Montana, where SPC has the Slight Risk for Wednesday. Am
thinking that the potential for the strongest storms will be along
and east of a Havre-to-Stanford line, as that appears to be the
favored area for wind shear and instability due to the position of
the frontal boundary. However, isolated severe storms are possible
west of this line as well, though they may be more marginally
severe. Have therefore continued the damaging wind/large
hail/heavy rainfall wording for these areas. Precipitation from
these storms may be exceptionally heavy in the aforementioned
eastern areas, adding the potential for flash flooding as well
(please see Hydrology section for details). The system will lift
northeast across the area later Wednesday night and into Thursday.
This will shift the flow aloft more westerly, but it will remain
moist, so have kept high POPs in the mountains. However, the
resulting strong westerly down-slope winds will hinder
shower/thunderstorm development over the plains. Winds aloft
become marginally strong along the Rocky Mountain Front on
Thursday, so will need to monitor this for possible high wind
highlights there. Temperatures will begin to cool closer to
normal from the west on Wednesday as the frontal boundary moves
through the area and showers become more widespread. In the wake
of the front, temperatures will cool to around 10 degrees below
normal by Thursday, which may cause snow to fall at elevations
above 6500 feet. Coulston
Thursday night through Tuesday...No significant changes made to
the medium range forecast. An unsettled pattern will persist
through Saturday as a closed upper low will remain quasi-
stationary over northwest Montana. Short wave energy will
continue to rotate out from the base of the low and help initiate
shower and thunderstorm development each day. The strength of
these storms will depend on availability of low level moisture
and the strength of the divergent flow aloft. The models also
continue to differ on the upper low`s position which, in turn,
will affect where and how strong thunderstorms will be. Because
of these differences, have continued to broad-brush the pops
through Saturday. By late Saturday, the models move the low to
northeast Montana and lift it out as an upper ridge begins
building over the Pacific Northwest. The ridge breaks down on
Sunday as short wave energy ripples across the area within the
westerly flow aloft. Isolated thunderstorms will remain a
possibility Sunday and Monday. By Tuesday, weak upper ridging
returns though isolated showers will persist over the southwest
mountains. Temperatures will remain below seasonal averages to
start the period due to cloud cover and periodic cold advection
from transient shortwaves. Temperatures should rise above
seasonal averages to start the week.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 85 54 76 46 / 60 60 80 80
CTB 83 51 73 45 / 70 70 100 90
HLN 86 52 75 46 / 60 50 70 60
BZN 86 47 79 42 / 30 30 50 40
WEY 78 37 70 32 / 20 20 30 20
DLN 84 48 71 39 / 40 40 60 50
HVR 86 59 83 51 / 20 50 80 90
LWT 83 53 79 44 / 30 40 60 80
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
weather.gov/greatfalls
000
FXUS65 KTFX 181620
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1020 AM MDT Tue Jun 18 2013
.UPDATE...
Minor updates to the forecast this morning. Adjusted POP a bit
based on current model data. Still expecting convective activity
with best chances developing over terrain this afternoon.
&&
.AVIATION...
Updated 1155Z.
Moist and unstable southwest flow aloft will continue. The air-mass
is unstable and will further destabilize after 17z. Strong
thunderstorms will develop after 20z and continue beyond 00z. Some
storms may become severe. VFR conditions prevail with MVFR
conditions possible in the vicinity of thunderstorms. Mountains and
higher terrain may be obscured at times after 20z.
&&
.HYDROLOGY...
More widespread showers and thunderstorms are possible along the
Rocky Mountain Front and adjacent plains today and over most of
the plains of north central/central Montana on Wednesday. Some of
these storms may produce brief heavy rainfall. These periods will
need to be monitored for possible areal flood/flash flood
highlights. The greater area of concern is across eastern portions
of north central and central Montana for Wednesday that still
have moist soil that would not be able to absorb much rapid
rainfall. However, if the rainfall from storms today are
significant along the Rocky Mountain Front, the additional rainfall
on Wednesday will increase the flooding threat there as well.
&&
.PREV DISCUSSION...
/ISSUED 555 AM MDT Tue Jun 18 2013/
Today through Thursday...Forecast models continue to indicate that
strong to possibly severe thunderstorms are possible both today
and Wednesday. As the Pacific low pressure system moves onto the
Pacific Northwest coast today, the flow aloft over western and
central Montana will become more moist, unstable, and
southwesterly. Temperatures will also warm to around 10 degrees
above normal. These factors will help generate showers and
thunderstorms over the higher terrain of these areas. The frontal
boundary associated with this system will also move into western
Montana today to provide a good focusing mechanism for storm
development. The flow aloft will also become more diffluent, which
should enhance vertical development of storms. These factors,
along with strong wind shear (both speed and directional) and
significant instability (CAPE values of 1500 to 2500 J/kg), the
Storm Prediction Center (SPC) has put portions of western and
central Montana under a Slight Risk for severe thunderstorms, and
we have subsequently added mention of damaging winds, large hail,
and heavy rainfall for this area. This area is generally northwest
of a Havre-to- Butte line. Thunderstorms will decrease overnight,
but another round of potentially severe weather is expected for
Wednesday as the system continues to move east across the Pacific
Northwest. The most unstable portion of the flow aloft and the
surface frontal boundary will also shift east into central and
eastern Montana, where SPC has the Slight Risk for Wednesday. Am
thinking that the potential for the strongest storms will be along
and east of a Havre-to-Stanford line, as that appears to be the
favored area for wind shear and instability due to the position of
the frontal boundary. However, isolated severe storms are possible
west of this line as well, though they may be more marginally
severe. Have therefore continued the damaging wind/large
hail/heavy rainfall wording for these areas. Precipitation from
these storms may be exceptionally heavy in the aforementioned
eastern areas, adding the potential for flash flooding as well
(please see Hydrology section for details). The system will lift
northeast across the area later Wednesday night and into Thursday.
This will shift the flow aloft more westerly, but it will remain
moist, so have kept high POPs in the mountains. However, the
resulting strong westerly down-slope winds will hinder
shower/thunderstorm development over the plains. Winds aloft
become marginally strong along the Rocky Mountain Front on
Thursday, so will need to monitor this for possible high wind
highlights there. Temperatures will begin to cool closer to
normal from the west on Wednesday as the frontal boundary moves
through the area and showers become more widespread. In the wake
of the front, temperatures will cool to around 10 degrees below
normal by Thursday, which may cause snow to fall at elevations
above 6500 feet. Coulston
Thursday night through Tuesday...No significant changes made to
the medium range forecast. An unsettled pattern will persist
through Saturday as a closed upper low will remain quasi-
stationary over northwest Montana. Short wave energy will
continue to rotate out from the base of the low and help initiate
shower and thunderstorm development each day. The strength of
these storms will depend on availability of low level moisture
and the strength of the divergent flow aloft. The models also
continue to differ on the upper low`s position which, in turn,
will affect where and how strong thunderstorms will be. Because
of these differences, have continued to broad-brush the pops
through Saturday. By late Saturday, the models move the low to
northeast Montana and lift it out as an upper ridge begins
building over the Pacific Northwest. The ridge breaks down on
Sunday as short wave energy ripples across the area within the
westerly flow aloft. Isolated thunderstorms will remain a
possibility Sunday and Monday. By Tuesday, weak upper ridging
returns though isolated showers will persist over the southwest
mountains. Temperatures will remain below seasonal averages to
start the period due to cloud cover and periodic cold advection
from transient shortwaves. Temperatures should rise above
seasonal averages to start the week.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 85 54 76 46 / 60 60 80 80
CTB 83 51 73 45 / 70 70 100 90
HLN 86 52 75 46 / 60 50 70 60
BZN 86 47 79 42 / 30 30 50 40
WEY 78 37 70 32 / 20 20 30 20
DLN 84 48 71 39 / 40 40 60 50
HVR 86 59 83 51 / 20 50 80 90
LWT 83 53 79 44 / 30 40 60 80
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
weather.gov/greatfalls
000
FXUS65 KTFX 181156
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
555 AM MDT Tue Jun 18 2013
UPDATED AVIATION SECTION
...Strong to possibly severe thunderstorms today and Wednesday...
.DISCUSSION...
Today through Thursday...Forecast models continue to indicate that
strong to possibly severe thunderstorms are possible both today
and Wednesday. As the Pacific low pressure system moves onto the
Pacific Northwest coast today, the flow aloft over western and
central Montana will become more moist, unstable, and
southwesterly. Temperatures will also warm to around 10 degrees
above normal. These factors will help generate showers and
thunderstorms over the higher terrain of these areas. The frontal
boundary associated with this system will also move into western
Montana today to provide a good focusing mechanism for storm
development. The flow aloft will also become more diffluent, which
should enhance vertical development of storms. These factors,
along with strong wind shear (both speed and directional) and
significant instability (CAPE values of 1500 to 2500 J/kg), the
Storm Prediction Center (SPC) has put portions of western and
central Montana under a Slight Risk for severe thunderstorms, and
we have subsequently added mention of damaging winds, large hail,
and heavy rainfall for this area. This area is generally northwest
of a Havre-to- Butte line. Thunderstorms will decrease overnight,
but another round of potentially severe weather is expected for
Wednesday as the system continues to move east across the Pacific
Northwest. The most unstable portion of the flow aloft and the
surface frontal boundary will also shift east into central and
eastern Montana, where SPC has the Slight Risk for Wednesday. Am
thinking that the potential for the strongest storms will be along
and east of a Havre-to-Stanford line, as that appears to be the
favored area for wind shear and instability due to the position of
the frontal boundary. However, isolated severe storms are possible
west of this line as well, though they may be more marginally
severe. Have therefore continued the damaging wind/large
hail/heavy rainfall wording for these areas. Precipitation from
these storms may be exceptionally heavy in the aforementioned
eastern areas, adding the potential for flash flooding as well
(please see Hydrology section for details). The system will lift
northeast across the area later Wednesday night and into Thursday.
This will shift the flow aloft more westerly, but it will remain
moist, so have kept high POPs in the mountains. However, the
resulting strong westerly downslope winds will hinder
shower/thunderstorm development over the plains. Winds aloft
become marginally strong along the Rocky Mountain Front on
Thursday, so will need to monitor this for possible high wind
highlights there. Temperatures will begin to cool closer to
normal from the west on Wednesday as the frontal boundary moves
through the area and showers become more widespread. In the wake
of the front, temperatures will cool to around 10 degrees below
normal by Thursday, which may cause snow to fall at elevations
above 6500 feet. Coulston
Thursday night through Tuesday...No significant changes made to
the medium range forecast. An unsettled pattern will persist
through Saturday as a closed upper low will remain quasi-
stationary over northwest Montana. Short wave energy will
continue to rotate out from the base of the low and help initiate
shower and thunderstorm development each day. The strength of
these storms will depend on availability of low level moisture
and the strength of the divergent flow aloft. The models also
continue to differ on the upper low`s position which, in turn,
will affect where and how strong thunderstorms will be. Because
of these differences, have continued to broadbrush the pops
through Saturday. By late Saturday, the models move the low to
northeast Montana and lift it out as an upper ridge begins
building over the Pacific Northwest. The ridge breaks down on
Sunday as short wave energy ripples across the area within the
westerly flow aloft. Isolated thunderstorms will remain a
possibility Sunday and Monday. By Tuesday, weak upper ridging
returns though isolated showers will persist over the southwest
mountains. Temperatures will remain below seasonal averages to
start the period due to cloud cover and periodic cold advection
from transient shortwaves. Temperatures should rise above
seasonal averages to start the week.
&&
.AVIATION...
Updated 1155Z.
Moist and unstable southwest flow aloft will continue. The airmass
is unstable and will further destabilize after 17z. Strong
thunderstorms will develop after 20z and continue beyond 00z. Some
storms may become severe. VFR conditions prevail with MVFR
conditions possible in the vicinity of thunderstorms. Mountains and
higher terrain may be obscured at times after 20z.
&&
.HYDROLOGY...
More widespread showers and thunderstorms are possible along the
Rocky Mountain Front and adjacent plains today and over most of
the plains of north central/central Montana on Wednesday. Some of
these storms may produce brief heavy rainfall. These periods will
need to be monitored for possible areal flood/flash flood
highlights. The greater area of concern is across eastern portions
of north central and central Montana for Wednesday that still
have moist soil that would not be able to absorb much rapid
rainfall. However, if the rainfall from storms today are
significant along the Rocky Mountain Front, the additional rainfall
on Wednesday will increase the flooding threat there as well.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 85 54 76 46 / 60 60 80 80
CTB 83 51 73 45 / 70 70 100 90
HLN 86 52 75 46 / 60 50 70 60
BZN 86 47 79 42 / 40 30 50 40
WEY 78 37 70 32 / 30 20 30 20
DLN 84 48 71 39 / 40 40 60 50
HVR 86 59 83 51 / 20 50 80 90
LWT 82 53 79 44 / 40 40 60 80
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...COULSTON
LONG TERM...EMANUEL
AVIATION...EMANUEL
weather.gov/greatfalls
000
FXUS65 KTFX 181042
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
442 AM MDT Tue Jun 18 2013
...Strong to possibly severe thunderstorms today and Wednesday...
.DISCUSSION...
Today through Thursday...Forecast models continue to indicate that
strong to possibly severe thunderstorms are possible both today
and Wednesday. As the Pacific low pressure system moves onto the
Pacific Northwest coast today, the flow aloft over western and
central Montana will become more moist, unstable, and
southwesterly. Temperatures will also warm to around 10 degrees
above normal. These factors will help generate showers and
thunderstorms over the higher terrain of these areas. The frontal
boundary associated with this system will also move into western
Montana today to provide a good focusing mechanism for storm
development. The flow aloft will also become more diffluent, which
should enhance vertical development of storms. These factors,
along with strong wind shear (both speed and directional) and
significant instability (CAPE values of 1500 to 2500 J/kg), the
Storm Prediction Center (SPC) has put portions of western and
central Montana under a Slight Risk for severe thunderstorms, and
we have subsequently added mention of damaging winds, large hail,
and heavy rainfall for this area. This area is generally northwest
of a Havre-to- Butte line. Thunderstorms will decrease overnight,
but another round of potentially severe weather is expected for
Wednesday as the system continues to move east across the Pacific
Northwest. The most unstable portion of the flow aloft and the
surface frontal boundary will also shift east into central and
eastern Montana, where SPC has the Slight Risk for Wednesday. Am
thinking that the potential for the strongest storms will be along
and east of a Havre-to-Stanford line, as that appears to be the
favored area for wind shear and instability due to the position of
the frontal boundary. However, isolated severe storms are possible
west of this line as well, though they may be more marginally
severe. Have therefore continued the damaging wind/large
hail/heavy rainfall wording for these areas. Precipitation from
these storms may be exceptionally heavy in the aforementioned
eastern areas, adding the potential for flash flooding as well
(please see Hydrology section for details). The system will lift
northeast across the area later Wednesday night and into Thursday.
This will shift the flow aloft more westerly, but it will remain
moist, so have kept high POPs in the mountains. However, the
resulting strong westerly downslope winds will hinder
shower/thunderstorm development over the plains. Winds aloft
become marginally strong along the Rocky Mountain Front on
Thursday, so will need to monitor this for possible high wind
highlights there. Temperatures will begin to cool closer to
normal from the west on Wednesday as the frontal boundary moves
through the area and showers become more widespread. In the wake
of the front, temperatures will cool to around 10 degrees below
normal by Thursday, which may cause snow to fall at elevations
above 6500 feet. Coulston
Thursday night through Tuesday...No significant changes made to
the medium range forecast. An unsettled pattern will persist
through Saturday as a closed upper low will remain quasi-
stationary over northwest Montana. Short wave energy will
continue to rotate out from the base of the low and help initiate
shower and thunderstorm development each day. The strength of
these storms will depend on availability of low level moisture
and the strength of the divergent flow aloft. The models also
continue to differ on the upper low`s position which, in turn,
will affect where and how strong thunderstorms will be. Because
of these differences, have continued to broadbrush the pops
through Saturday. By late Saturday, the models move the low to
northeast Montana and lift it out as an upper ridge begins
building over the Pacific Northwest. The ridge breaks down on
Sunday as short wave energy ripples across the area within the
westerly flow aloft. Isolated thunderstorms will remain a
possibility Sunday and Monday. By Tuesday, weak upper ridging
returns though isolated showers will persist over the southwest
mountains. Temperatures will remain below seasonal averages to
start the period due to cloud cover and periodic cold advection
from transient shortwaves. Temperatures should rise above
seasonal averages to start the week.
&&
.AVIATION...
Updated 0455Z.
Scattered showers and thunderstorms will continue to move across
central Montana through 09Z with the KHLN and KLWT areas most likely
to see convective activity. Skies will clear out by 12Z but another
round of strong and possibly severe thunderstorms will develop after
20Z and continue into the late evening. VFR conditions will prevail
but conditions may deteriorate to MVFR in heavy rainfall associated
with the strongest storms. mpj
&&
.HYDROLOGY...
More widespread showers and thunderstorms are possible along the
Rocky Mountain Front and adjacent plains today and over most of
the plains of north central/central Montana on Wednesday. Some of
these storms may produce brief heavy rainfall. These periods will
need to be monitored for possible areal flood/flash flood
highlights. The greater area of concern is across eastern portions
of north central and central Montana for Wednesday that still
have moist soil that would not be able to absorb much rapid
rainfall. However, if the rainfall from storms today are
significant along the Rocky Mountain Front, the additional
rainfall on Wednesday will increase the flooding threat there.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 85 54 76 46 / 60 60 80 80
CTB 83 51 73 45 / 70 70 100 90
HLN 86 52 75 46 / 60 50 70 60
BZN 86 47 79 42 / 40 30 50 40
WEY 78 37 70 32 / 30 20 30 20
DLN 84 48 71 39 / 40 40 60 50
HVR 86 59 83 51 / 20 50 80 90
LWT 82 53 79 44 / 40 40 60 80
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...COULSTON
LONG TERM...EMANUEL
AVIATION...mpj
weather.gov/greatfalls
000
FXUS65 KTFX 180451
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1055 PM MDT Mon Jun 17 2013
...UPDATE TO AVIATION...
.UPDATE...
Current forecast is on track...with just a minor adjustment to
pops overnight. Isolated thunderstorms continue to redevelop over
Southwest MT and move northeastward into Central/North Central MT.
Thus I added some isolated thunderstorms overnight generally along
the path the storms have been taking through the evening hours.
Most storms should only produce brief heavy rainfall...lightning
and small hail overnight. Overnight lows look on track.
Looking ahead...it should be a bit more active for severe weather
on Tue and Wed across much of the region. SPC has a slight risk of
severe weather both days over portions of Central and North
Central MT and that looks good. Brusda
&&
.AVIATION...
Updated 0455Z.
Scattered showers and thunderstorms will continue to move across
central Montana through 09Z with the KHLN and KLWT areas most likely
to see convective activity. Skies will clear out by 12Z but another
round of strong and possibly severe thunderstorms will develop after
20Z and continue into the late evening. VFR conditions will prevail
but conditions may deteriorate to MVFR in heavy rainfall associated
with the strongest storms. mpj
&&
.HYDROLOGY...
A stronger period of showers and thunderstorms are possible on
Wednesday, which may produce brief heavy rainfall. In fact, this
situation will likely need to be monitored for possible areal
flood/flash flood highlights across portions of north central and
central Montana that still have moist soil that would not be able
to absorb much rapid rainfall.
&&
.PREV DISCUSSION...
/ISSUED 543 PM MDT Mon Jun 17 2013/
Tonight through Wednesday...The high pressure ridge will continue to
keep the airmass relatively dry and shower/thunderstorm activity
will diminish this evening. The ridge will move east of the zones
Tuesday and a low pressure system over the Eastern Pacific will
move over the West Coast. This will put central Montana underneath
moist, unsettled southwest flow aloft. The airmass will become
unstable during the day and a cold front will be crossing the
Rockies late afternoon and evening. Scattered thunderstorms are
expected across most of the region with numerous storms over the
Rockies and adjacent slopes. Convection may last well into Tuesday
evening along the eastern zones due to the slow eastward movement of
the cold front. The low pressure system will continue to approach
the region and heights aloft will continue to fall. and
thunderstorm activity will increase Wednesday as the airmass becomes
very moist and unstable. Heavy rain is possible across the central
and northern portions of the region, and large hail possible over
the northeastern zones.
Wednesday night through Monday...A somewhat unsettled pattern will
characterize the long term forecast. A low pressure system will push
slowly drift across the Pacific Northwest through the long term.
Shortwave energy will continue to rotate out from the main trough
and move across the area from the southwest. Scattered showers
and thunderstorms will continue to develop over Southwest Montana
and then move northeast across Central Montana. The system will
reach Northwest Montana Thursday morning before stalling and slowly
weakening. The low will lift out over southern Saskatchewan Sunday.
The models develop differences in their solutions by Monday with the
ECMWF building a ridge and the GFS maintaining weak cyclonic flow
over Montana. Uncertainty with the timing and placement of
convective activity has led to a broad-brushed approach with regards
to POP grids during the period. Due to cloud cover and periodic
advection of cooler air following shortwaves, temperatures will
remain generally below seasonal averages through Saturday. Highs
should climb above seasonal averages to start the week.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 51 84 53 74 / 20 40 40 80
CTB 48 82 50 70 / 20 50 60 90
HLN 51 84 51 73 / 30 50 30 70
BZN 45 85 45 76 / 20 50 30 60
WEY 38 77 37 69 / 20 40 10 60
DLN 47 82 47 68 / 30 40 30 70
HVR 54 87 57 80 / 20 30 30 90
LWT 49 82 53 79 / 10 40 50 70
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
weather.gov/greatfalls
000
FXUS65 KTFX 180317
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
917 PM MDT Mon Jun 17 2013
.UPDATE...
Current forecast is on track...with just a minor adjustment to
pops overnight. Isolated thunderstorms continue to redevelop over
Southwest MT and move northeastward into Central/North Central MT.
Thus I added some isolated thunderstorms overnight generally along
the path the storms have been taking through the evening hours.
Most storms should only produce brief heavy rainfall...lightning
and small hail overnight. Overnight lows look on track.
Looking ahead...it should be a bit more active for severe weather
on Tue and Wed across much of the region. SPC has a slight risk of
severe weather both days over portions of Central and North
Central MT and that looks good. Brusda
&&
.AVIATION...
Updated 2343Z.
VFR conditions will prevail through the period. Existing late
afternoon showers will dissipate by 03Z, with light winds and few
clouds overnight. Southwest flow aloft will destabilize after 18Z
Tuesday with showers and thunderstorms probable KBZN/KHLN/KCTB/KGTF
after 20Z. This activity will develop first over higher terrain and
move east to northeast. Showers will push further east to affect
KHVR/KLWT around 19/00Z. MVFR conditions may be possible in the
vicinity of showers and thunderstorms. Nutter
&&
.HYDROLOGY...
A stronger period of showers and thunderstorms are possible on
Wednesday, which may produce brief heavy rainfall. In fact, this
situation will likely need to be monitored for possible areal
flood/flash flood highlights across portions of north central and
central Montana that still have moist soil that would not be able
to absorb much rapid rainfall.
&&
.PREV DISCUSSION...
/ISSUED 543 PM MDT Mon Jun 17 2013/
Tonight through Wednesday...The high pressure ridge will continue to
keep the airmass relatively dry and shower/thunderstorm activity
will diminish this evening. The ridge will move east of the zones
Tuesday and a low pressure system over the Eastern Pacific will
move over the West Coast. This will put central Montana underneath
moist, unsettled southwest flow aloft. The airmass will become
unstable during the day and a cold front will be crossing the
Rockies late afternoon and evening. Scattered thunderstorms are
expected across most of the region with numerous storms over the
Rockies and adjacent slopes. Convection may last well into Tuesday
evening along the eastern zones due to the slow eastward movement of
the cold front. The low pressure system will continue to approach
the region and heights aloft will continue to fall. and
thunderstorm activity will increase Wednesday as the airmass becomes
very moist and unstable. Heavy rain is possible across the central
and northern portions of the region, and large hail possible over
the northeastern zones.
Wednesday night through Monday...A somewhat unsettled pattern will
characterize the long term forecast. A low pressure system will push
slowly drift across the Pacific Northwest through the long term.
Shortwave energy will continue to rotate out from the main trough
and move across the area from the southwest. Scattered showers
and thunderstorms will continue to develop over Southwest Montana
and then move northeast across Central Montana. The system will
reach Northwest Montana Thursday morning before stalling and slowly
weakening. The low will lift out over southern Saskatchewan Sunday.
The models develop differences in their solutions by Monday with the
ECMWF building a ridge and the GFS maintaining weak cyclonic flow
over Montana. Uncertainty with the timing and placement of
convective activity has led to a broad-brushed approach with regards
to POP grids during the period. Due to cloud cover and periodic
advection of cooler air following shortwaves, temperatures will
remain generally below seasonal averages through Saturday. Highs
should climb above seasonal averages to start the week.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 51 84 53 74 / 20 40 40 80
CTB 48 82 50 70 / 20 50 60 90
HLN 51 84 51 73 / 30 50 30 70
BZN 45 85 45 76 / 20 50 30 60
WEY 38 77 37 69 / 20 40 10 60
DLN 47 82 47 68 / 30 40 30 70
HVR 54 87 57 80 / 20 30 30 90
LWT 49 82 53 79 / 10 40 50 70
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
weather.gov/greatfalls
000
FXUS65 KTFX 172343
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
543 PM MDT Mon Jun 17 2013
Aviation Section Updated
.DISCUSSION...
Tonight through Wednesday...The high pressure ridge will continue to
keep the airmass relatively dry and shower/thunderstorm activity
will diminish this evening. The ridge will move east of the zones
Tuesday and a low pressure system over the Eastern Pacific will
move over the West Coast. This will put central Montana underneath
moist, unsettled southwest flow aloft. The airmass will become
unstable during the day and a cold front will be crossing the
Rockies late afternoon and evening. Scattered thunderstorms are
expected across most of the region with numerous storms over the
Rockies and adjacent slopes. Convection may last well into Tuesday
evening along the eastern zones due to the slow eastward movement of
the cold front. The low pressure system will continue to approach
the region and heights aloft will continue to fall. and
thunderstorm activity will increase Wednesday as the airmass becomes
very moist and unstable. Heavy rain is possible across the central
and northern portions of the region, and large hail possible over
the northeastern zones.
Wednesday night through Monday...A somewhat unsettled pattern will
characterize the long term forecast. A low pressure system will push
slowly drift across the Pacific Northwest through the long term.
Shortwave energy will continue to rotate out from the main trough
and move across the area from the southwest. Scattered showers
and thunderstorms will continue to develop over Southwest Montana
and then move northeast across Central Montana. The system will
reach Northwest Montana Thursday morning before stalling and slowly
weakening. The low will lift out over southern Saskatchewan Sunday.
The models develop differences in their solutions by Monday with the
ECMWF building a ridge and the GFS maintaining weak cyclonic flow
over Montana. Uncertainty with the timing and placement of
convective activity has led to a broad-brushed approach with regards
to POP grids during the period. Due to cloud cover and periodic
advection of cooler air following shortwaves, temperatures will
remain generally below seasonal averages through Saturday. Highs
should climb above seasonal averages to start the week.
&&
.AVIATION...
Updated 2343Z.
VFR conditions will prevail through the period. Existing late
afternoon showers will dissipate by 03Z, with light winds and few
clouds overnight. Southwest flow aloft will destabilize after 18Z
Tuesday with showers and thunderstorms probable KBZN/KHLN/KCTB/KGTF
after 20Z. This activity will develop first over higher terrain and
move east to northeast. Showers will push further east to affect
KHVR/KLWT around 19/00Z. MVFR conditions may be possible in the
vicinity of showers and thunderstorms. Nutter
&&
.HYDROLOGY...
A stronger period of showers and thunderstorms are possible on
Wednesday, which may produce brief heavy rainfall. In fact, this
situation will likely need to be monitored for possible areal
flood/flash flood highlights across portions of north central and
central Montana that still have moist soil that would not be able to
absorb much rapid rainfall.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 51 84 53 74 / 20 40 40 80
CTB 48 82 50 70 / 20 50 60 90
HLN 51 84 51 73 / 30 50 30 70
BZN 45 85 45 76 / 20 50 30 60
WEY 38 77 37 69 / 20 40 10 60
DLN 47 82 47 68 / 20 40 30 70
HVR 54 87 57 80 / 10 30 30 90
LWT 49 82 53 79 / 20 40 50 70
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
Flood warning continues for Big Sandy Creek near Havre until
further notice.
&&
$$
weather.gov/greatfalls
000
FXUS65 KTFX 172104
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
304 PM MDT Mon Jun 17 2013
.DISCUSSION...
Tonight through Wednesday...The high pressure ridge will continue to
keep the airmass relatively dry and shower/thunderstorm activity
will diminish this evening. The ridge will move east of the zones
Tuesday and a low pressure system over the Eastern Pacific will
move over the West Coast. This will put central Montana underneath
moist, unsettled southwest flow aloft. The airmass will become
unstable during the day and a cold front will be crossing the
Rockies late afternoon and evening. Scattered thunderstorms are
expected across most of the region with numerous storms over the
Rockies and adjacent slopes. Convection may last well into Tuesday
evening along the eastern zones due to the slow eastward movement of
the cold front. The low pressure system will continue to approach
the region and heights aloft will continue to fall. and
thunderstorm activity will increase Wednesday as the airmass becomes
very moist and unstable. Heavy rain is possible across the central
and northern portions of the region, and large hail possible over
the northeastern zones.
Wednesday night through Monday...A somewhat unsettled pattern will
characterize the long term forecast. A low pressure system will push
slowly drift across the Pacific Northwest through the long term.
Shortwave energy will continue to rotate out from the main trough
and move across the area from the southwest. Scattered showers
and thunderstorms will continue to develop over Southwest Montana
and then move northeast across Central Montana. The system will
reach Northwest Montana Thursday morning before stalling and slowly
weakening. The low will lift out over southern Saskatchewan Sunday.
The models develop differences in their solutions by Monday with the
ECMWF building a ridge and the GFS maintaining weak cyclonic flow
over Montana. Uncertainty with the timing and placement of
convective activity has led to a broad-brushed approach with regards
to POP grids during the period. Due to cloud cover and periodic
advection of cooler air following shortwaves, temperatures will
remain generally below seasonal averages through Saturday. Highs
should climb above seasonal averages to start the week.
&&
.AVIATION...
Updated 1800Z.
Southwest flow will continue to bring moisture and instability to
Central Montana. Conditions will destabilize after 18z with a few
showers and isolated thunderstorms possible after 22z. Showers will
develop over terrain and may slowly drift over the plains. Activity
should generally end by 06z. VFR conditions prevail with MVFR
conditions possible in the vicinity of showers and thunderstorms.
&&
.HYDROLOGY...
A stronger period of showers and thunderstorms are possible on
Wednesday, which may produce brief heavy rainfall. In fact, this
situation will likely need to be monitored for possible areal
flood/flash flood highlights across portions of north central and
central Montana that still have moist soil that would not be able to
absorb much rapid rainfall.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 51 84 53 74 / 20 40 40 80
CTB 48 82 50 70 / 20 50 60 90
HLN 51 84 51 73 / 30 50 30 70
BZN 45 85 45 76 / 20 50 30 60
WEY 38 77 37 69 / 20 40 10 60
DLN 47 82 47 68 / 20 40 30 70
HVR 54 87 57 80 / 10 30 30 90
LWT 49 82 53 79 / 20 40 50 70
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
Flood warning continues for Big Sandy Creek near Havre until
further notice.
&&
$$
weather.gov/greatfalls
000
FXUS65 KTFX 171819
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1200 PM MDT Mon Jun 17 2013
.UPDATE...
Today...The region will be underneath an upper level high pressure
today. The airmass will become slightly unstable this afternoon but
convective temperatures will not be reached until late...so most
convection will be at higher elevations. Current forecast on
track. Zelzer
&&
.AVIATION...
Updated 1800Z.
Southwest flow will continue to bring moisture and instability to
Central Montana. Conditions will destabilize after 18z with a few
showers and isolated thunderstorms possible after 22z. Showers will
develop over terrain and may slowly drift over the plains. Activity
should generally end by 06z. VFR conditions prevail with MVFR
conditions possible in the vicinity of showers and thunderstorms.
&&
.HYDROLOGY...
A point flood warning remains in effect for the Big Sandy Creek
near Havre. A few afternoon/evening showers/thunderstorms are
possible through Tuesday of this week, but they should not impact
the river level there significantly. The level should very
gradually decrease through the early part of the week, but it is
expected to remain above flood stage. However, stronger
thunderstorms are possible on Wednesday, which may produce brief
heavy rainfall. If one of these thunderstorms drops heavy rain
near the creek, it may cause additional flooding problems. In
fact, this situation will likely need to be monitored for possible
areal flood/flash flood highlights across portions of north
central and central Montana that still have moist soil that would
not be able to absorb much rapid rainfall.
&&
.PREV DISCUSSION...
/ISSUED 540 AM MDT Mon Jun 17 2013/
Today through Wednesday...A Pacific low pressure system will
dictate the weather across north central and southwest Montana
during this period. The system will slowly move onto the Pacific
Northwest coast through Tuesday night. As a result, the upper
level ridge of high pressure currently over the area will shift
east across the state, allowing an increasingly moist and unstable
southwesterly flow aloft to move overhead. Isolated showers and
thunderstorms will likely develop this afternoon/evening over the
mountain areas of western and southwest Montana and then move out
over the plains. The lower and mid levels of the atmosphere will
remain fairly dry, as temperatures warm to around 5 degrees above
normal, making gusty winds the main threat from these storms.
Wind shear will be weak, but winds shifting from easterly at the
surface to more westerly aloft may provide enough directional
shear to make a few of the storms strong. Increasing winds aloft,
moisture, and instability will combine with 5 to 10 degree warmer
temperatures to bring the potential for more and stronger
thunderstorms on Tuesday. Again, gusty winds will be the main
threat, but the increasing moisture and shear may also cause small
hail from some storms. Wednesday still appears to have the
greatest potential for severe weather, mainly over the plains of
north central and central Montana (SPC currently has this area
under a Slight Risk designation for severe weather). The Pacific
low pressure system is forecast to move into the Pacific
Northwest, causing the flow aloft to become more southerly and
diffluent and increasing the storm growth potential. Also,
precipitable water values increase to over 1 inch across eastern
portions of the forecast area, which is significantly above normal
for this time of year. This indicates the potential for heavy
rainfall and large hail. A cold front is also forecast to move
across the area Wednesday afternoon, but anecdotal evidence
suggests that the frontal passage may be slower than forecast.
Taking this into consideration, southeasterly winds should
increase ahead of the front over the plains, providing strong
speed and directional wind shear, which should help promote storm
rotation/growth and strong wind gusts. Have therefore addressed
this possibility in the forecast wording for Wednesday. Although
forecast storm-relative helicity is low (due to faster eastward
movement of the front), if the cold front does in fact slow down,
the strong wind shear may introduce the potential for an isolated
tornado in the easternmost TFX zones (Hill/Blaine/Chouteau/Fergus
counties). Will continue to monitor this potential. Coulston
Wednesday night through Monday...An unsettled pattern will
characterize the medium range period. An upper closed low will
push slowly across the Pacific Northwest. Shortwave energy will
continue to rotate out from the low and move across the area
embedded within the southwest flow aloft. Scattered showers and
thunderstorms will continue to develop over southwest Montana and
then move north and east across the plains. The upper low will
reach northwest Montana by Thursday morning and then stall and
slowly fill. By the weekend, the low will lift out over southern
Saskatchewan. The models develop differences in their solutions
by late in the weekend. The European builds an upper ridge Sunday
and Monday while the GFS maintains weak cyclonic flow over the
area. Uncertainty with the timing and placement of convective
activity has led to a broadbrushed approach with regards to pops
during the period. Due to cloud cover and periodic advection of
cooler air following shortwave passages, temperatures will remain
generally below seasonal averages through Saturday. Afternoon
readings should climb above seasonal averages to start the week.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 80 54 86 56 / 20 30 50 30
CTB 80 51 84 56 / 20 20 50 40
HLN 84 52 88 54 / 20 30 50 30
BZN 83 46 86 49 / 20 20 30 20
WEY 76 36 78 38 / 20 20 30 20
DLN 82 47 83 49 / 20 20 30 20
HVR 80 58 89 61 / 10 10 10 40
LWT 76 51 84 54 / 20 20 40 40
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
Flood warning continues for Big Sandy Creek near Havre until
further notice.
&&
$$
weather.gov/greatfalls
000
FXUS65 KTFX 171547
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
947 AM MDT Mon Jun 17 2013
.UPDATE...
Today...The region will be underneath an upper level high pressure
today. The airmass will become slightly unstable this afternoon but
convective temperatures will not be reached until late...so most
convection will be at higher elevations. Current forecast on
track. Zelzer
&&
.AVIATION...
Updated 1140Z.
Increasing southwest flow aloft will continue to bring moisture and
instability to the area. The airmass will begin to destabilize after
18z and isolated thunderstorms are possible after 21z. Convective
activity should generally end by 06z. VFR conditions prevail with
MVFR conditions possible in the vicinity of thunderstorms.
&&
.HYDROLOGY...
A point flood warning remains in effect for the Big Sandy Creek
near Havre. A few afternoon/evening showers/thunderstorms are
possible through Tuesday of this week, but they should not impact
the river level there significantly. The level should very
gradually decrease through the early part of the week, but it is
expected to remain above flood stage. However, stronger
thunderstorms are possible on Wednesday, which may produce brief
heavy rainfall. If one of these thunderstorms drops heavy rain
near the creek, it may cause additional flooding problems. In
fact, this situation will likely need to be monitored for possible
areal flood/flash flood highlights across portions of north
central and central Montana that still have moist soil that would
not be able to absorb much rapid rainfall.
&&
.PREV DISCUSSION...
/ISSUED 540 AM MDT Mon Jun 17 2013/
Today through Wednesday...A Pacific low pressure system will
dictate the weather across north central and southwest Montana
during this period. The system will slowly move onto the Pacific
Northwest coast through Tuesday night. As a result, the upper
level ridge of high pressure currently over the area will shift
east across the state, allowing an increasingly moist and unstable
southwesterly flow aloft to move overhead. Isolated showers and
thunderstorms will likely develop this afternoon/evening over the
mountain areas of western and southwest Montana and then move out
over the plains. The lower and mid levels of the atmosphere will
remain fairly dry, as temperatures warm to around 5 degrees above
normal, making gusty winds the main threat from these storms.
Wind shear will be weak, but winds shifting from easterly at the
surface to more westerly aloft may provide enough directional
shear to make a few of the storms strong. Increasing winds aloft,
moisture, and instability will combine with 5 to 10 degree warmer
temperatures to bring the potential for more and stronger
thunderstorms on Tuesday. Again, gusty winds will be the main
threat, but the increasing moisture and shear may also cause small
hail from some storms. Wednesday still appears to have the
greatest potential for severe weather, mainly over the plains of
north central and central Montana (SPC currently has this area
under a Slight Risk designation for severe weather). The Pacific
low pressure system is forecast to move into the Pacific
Northwest, causing the flow aloft to become more southerly and
diffluent and increasing the storm growth potential. Also,
precipitable water values increase to over 1 inch across eastern
portions of the forecast area, which is significantly above normal
for this time of year. This indicates the potential for heavy
rainfall and large hail. A cold front is also forecast to move
across the area Wednesday afternoon, but anecdotal evidence
suggests that the frontal passage may be slower than forecast.
Taking this into consideration, southeasterly winds should
increase ahead of the front over the plains, providing strong
speed and directional wind shear, which should help promote storm
rotation/growth and strong wind gusts. Have therefore addressed
this possibility in the forecast wording for Wednesday. Although
forecast storm-relative helicity is low (due to faster eastward
movement of the front), if the cold front does in fact slow down,
the strong wind shear may introduce the potential for an isolated
tornado in the easternmost TFX zones (Hill/Blaine/Chouteau/Fergus
counties). Will continue to monitor this potential. Coulston
Wednesday night through Monday...An unsettled pattern will
characterize the medium range period. An upper closed low will
push slowly across the Pacific Northwest. Shortwave energy will
continue to rotate out from the low and move across the area
embedded within the southwest flow aloft. Scattered showers and
thunderstorms will continue to develop over southwest Montana and
then move north and east across the plains. The upper low will
reach northwest Montana by Thursday morning and then stall and
slowly fill. By the weekend, the low will lift out over southern
Saskatchewan. The models develop differences in their solutions
by late in the weekend. The European builds an upper ridge Sunday
and Monday while the GFS maintains weak cyclonic flow over the
area. Uncertainty with the timing and placement of convective
activity has led to a broadbrushed approach with regards to pops
during the period. Due to cloud cover and periodic advection of
cooler air following shortwave passages, temperatures will remain
generally below seasonal averages through Saturday. Afternoon
readings should climb above seasonal averages to start the week.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 80 54 86 56 / 20 30 50 30
CTB 80 51 84 56 / 20 20 50 40
HLN 84 52 88 54 / 20 30 50 30
BZN 83 46 86 49 / 20 20 30 20
WEY 76 36 78 38 / 20 20 30 20
DLN 82 47 83 49 / 20 20 30 20
HVR 80 58 89 61 / 10 10 10 40
LWT 76 51 84 54 / 20 20 40 40
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
Flood warning continues for Big Sandy Creek near Havre until
further notice.
&&
$$
weather.gov/greatfalls
000
FXUS65 KTFX 171140
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
540 AM MDT Mon Jun 17 2013
UPDATED AVIATION SECTION
...Strong thunderstorms Tuesday with some possibly severe
Wednesday...
.DISCUSSION...
Today through Wednesday...A Pacific low pressure system will
dictate the weather across north central and southwest Montana
during this period. The system will slowly move onto the Pacific
Northwest coast through Tuesday night. As a result, the upper
level ridge of high pressure currently over the area will shift
east across the state, allowing an increasingly moist and unstable
southwesterly flow aloft to move overhead. Isolated showers and
thunderstorms will likely develop this afternoon/evening over the
mountain areas of western and southwest Montana and then move out
over the plains. The lower and mid levels of the atmosphere will
remain fairly dry, as temperatures warm to around 5 degrees above
normal, making gusty winds the main threat from these storms.
Wind shear will be weak, but winds shifting from easterly at the
surface to more westerly aloft may provide enough directional
shear to make a few of the storms strong. Increasing winds aloft,
moisture, and instability will combine with 5 to 10 degree warmer
temperatures to bring the potential for more and stronger
thunderstorms on Tuesday. Again, gusty winds will be the main
threat, but the increasing moisture and shear may also cause small
hail from some storms. Wednesday still appears to have the
greatest potential for severe weather, mainly over the plains of
north central and central Montana (SPC currently has this area
under a Slight Risk designation for severe weather). The Pacific
low pressure system is forecast to move into the Pacific
Northwest, causing the flow aloft to become more southerly and
diffluent and increasing the storm growth potential. Also,
precipitable water values increase to over 1 inch across eastern
portions of the forecast area, which is significantly above normal
for this time of year. This indicates the potential for heavy
rainfall and large hail. A cold front is also forecast to move
across the area Wednesday afternoon, but anecdotal evidence
suggests that the frontal passage may be slower than forecast.
Taking this into consideration, southeasterly winds should
increase ahead of the front over the plains, providing strong
speed and directional wind shear, which should help promote storm
rotation/growth and strong wind gusts. Have therefore addressed
this possibility in the forecast wording for Wednesday. Although
forecast storm-relative helicity is low (due to faster eastward
movement of the front), if the cold front does in fact slow down,
the strong wind shear may introduce the potential for an isolated
tornado in the easternmost TFX zones (Hill/Blaine/Chouteau/Fergus
counties). Will continue to monitor this potential. Coulston
Wednesday night through Monday...An unsettled pattern will
characterize the medium range period. An upper closed low will
push slowly across the Pacific Northwest. Shortwave energy will
continue to rotate out from the low and move across the area
embedded within the southwest flow aloft. Scattered showers and
thunderstorms will continue to develop over southwest Montana and
then move north and east across the plains. The upper low will
reach northwest Montana by Thursday morning and then stall and
slowly fill. By the weekend, the low will lift out over southern
Saskatchewan. The models develop differences in their solutions
by late in the weekend. The European builds an upper ridge Sunday
and Monday while the GFS maintains weak cyclonic flow over the
area. Uncertainty with the timing and placement of convective
activity has led to a broadbrushed approach with regards to pops
during the period. Due to cloud cover and periodic advection of
cooler air following shortwave passages, temperatures will remain
generally below seasonal averages through Saturday. Afternoon
readings should climb above seasonal averages to start the week.
&&
.AVIATION...
Updated 1140Z.
Increasing southwest flow aloft will continue to bring moisture and
instability to the area. The airmass will begin to destabilize after
18z and isolated thunderstorms are possible after 21z. Convective
activity should generally end by 06z. VFR conditions prevail with
MVFR conditions possible in the vicinity of thunderstorms.
&&
.HYDROLOGY...
A point flood warning remains in effect for the Big Sandy Creek
near Havre. A few afternoon/evening showers/thunderstorms are
possible through Tuesday of this week, but they should not impact
the river level there significantly. The level should very
gradually decrease through the early part of the week, but it is
expected to remain above flood stage. However, stronger
thunderstorms are possible on Wednesday, which may produce brief
heavy rainfall. If one of these thunderstorms drops heavy rain
near the creek, it may cause additional flooding problems. In
fact, this situation will likely need to be monitored for possible
areal flood/flash flood highlights across portions of north
central and central Montana that still have moist soil that would
not be able to absorb much rapid rainfall.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 80 54 86 56 / 20 30 50 30
CTB 80 51 84 56 / 20 20 50 40
HLN 84 52 88 54 / 20 30 50 30
BZN 83 46 86 49 / 20 20 30 20
WEY 76 36 78 38 / 20 20 30 20
DLN 82 47 83 49 / 20 20 30 20
HVR 80 58 89 61 / 10 10 10 40
LWT 76 51 84 54 / 20 20 40 40
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
Flood warning continues for Big Sandy Creek near Havre until
further notice.
&&
$$
SHORT TERM...COULSTON
LONG TERM...EMANUEL
AVIATION...EMANUEL
weather.gov/greatfalls
000
FXUS65 KTFX 171058
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
458 AM MDT Mon Jun 17 2013
...Strong thunderstorms Tuesday with some possibly severe
Wednesday...
.DISCUSSION...
Today through Wednesday...A Pacific low pressure system will
dictate the weather across north central and southwest Montana
during this period. The system will slowly move onto the Pacific
Northwest coast through Tuesday night. As a result, the upper
level ridge of high pressure currently over the area will shift
east across the state, allowing an increasingly moist and unstable
southwesterly flow aloft to move overhead. Isolated showers and
thunderstorms will likely develop this afternoon/evening over the
mountain areas of western and southwest Montana and then move out
over the plains. The lower and mid levels of the atmosphere will
remain fairly dry, as temperatures warm to around 5 degrees above
normal, making gusty winds the main threat from these storms.
Wind shear will be weak, but winds shifting from easterly at the
surface to more westerly aloft may provide enough directional
shear to make a few of the storms strong. Increasing winds aloft,
moisture, and instability will combine with 5 to 10 degree warmer
temperatures to bring the potential for more and stronger
thunderstorms on Tuesday. Again, gusty winds will be the main
threat, but the increasing moisture and shear may also cause small
hail from some storms. Wednesday still appears to have the
greatest potential for severe weather, mainly over the plains of
north central and central Montana (SPC currently has this area
under a Slight Risk designation for severe weather). The Pacific
low pressure system is forecast to move into the Pacific
Northwest, causing the flow aloft to become more southerly and
diffluent and increasing the storm growth potential. Also,
precipitable water values increase to over 1 inch across eastern
portions of the forecast area, which is significantly above normal
for this time of year. This indicates the potential for heavy
rainfall and large hail. A cold front is also forecast to move
across the area Wednesday afternoon, but anecdotal evidence
suggests that the frontal passage may be slower than forecast.
Taking this into consideration, southeasterly winds should
increase ahead of the front over the plains, providing strong
speed and directional wind shear, which should help promote storm
rotation/growth and strong wind gusts. Have therefore addressed
this possibility in the forecast wording for Wednesday. Although
forecast storm-relative helicity is low (due to faster eastward
movement of the front), if the cold front does in fact slow down,
the strong wind shear may introduce the potential for an isolated
tornado in the easternmost TFX zones (Hill/Blaine/Chouteau/Fergus
counties). Will continue to monitor this potential. Coulston
Wednesday night through Monday...An unsettled pattern will
characterize the medium range period. An upper closed low will
push slowly across the Pacific Northwest. Shortwave energy will
continue to rotate out from the low and move across the area
embedded within the southwest flow aloft. Scattered showers and
thunderstorms will continue to develop over southwest Montana and
then move north and east across the plains. The upper low will
reach northwest Montana by Thursday morning and then stall and
slowly fill. By the weekend, the low will lift out over southern
Saskatchewan. The models develop differences in their solutions
by late in the weekend. The European builds an upper ridge Sunday
and Monday while the GFS maintains weak cyclonic flow over the
area. Uncertainty with the timing and placement of convective
activity has led to a broadbrushed approach with regards to pops
during the period. Due to cloud cover and periodic advection of
cooler air following shortwave passages, temperatures will remain
generally below seasonal averages through Saturday. Afternoon
readings should climb above seasonal averages to start the week.
&&
.AVIATION...
Updated 0455Z.
Generally VFR conditions will prevail over the region through the
period. However...isolated evening showers/TS will affect far SW
MT this evening...mainly along a line from Butte to White Sulphur
Springs. This precipitation activity should diminish by 10z.
Expect new storms to redevelop after 21z on Monday over Southwest
MT. They will push northward towards Central MT by 00z Tue. Mainly
kept VCTS at the terminals for now on Monday afternoon...as TS
activity looks to be fairly isolated...and confidence is low right
now about any particular terminal being hit by a TS. Brusda
&&
.HYDROLOGY...
A point flood warning remains in effect for the Big Sandy Creek
near Havre. A few afternoon/evening showers/thunderstorms are
possible through Tuesday of this week, but they should not impact
the river level there significantly. The level should very
gradually decrease through the early part of the week, but it is
expected to remain above flood stage. However, stronger
thunderstorms are possible on Wednesday, which may produce brief
heavy rainfall. If one of these thunderstorms drops heavy rain
near the creek, it may cause additional flooding problems. In
fact, this situation will likely need to be monitored for possible
areal flood/flash flood highlights across portions of north
central and central Montana that still have moist soil that would
not be able to absorb much rapid rainfall.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 80 54 86 56 / 20 30 50 30
CTB 80 51 84 56 / 20 20 50 40
HLN 84 52 88 54 / 20 30 50 30
BZN 83 46 86 49 / 20 20 30 20
WEY 76 36 78 38 / 20 20 30 20
DLN 82 47 83 49 / 20 20 30 20
HVR 80 58 89 61 / 10 10 10 40
LWT 76 51 84 54 / 20 20 40 40
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
Flood warning continues for Big Sandy Creek near Havre until
further notice.
&&
$$
SHORT TERM...COULSTON
LONG TERM...EMANUEL
AVIATION...BRUSDA
weather.gov/greatfalls
000
FXUS65 KTFX 170452
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1055 PM MDT Sun Jun 16 2013
Aviation section updated
.UPDATE...
A few showers continue over southwest Montana at mid-evening but
now the main ones are over the northern portion of southwest
Montana whereas earlier they were over the southern portion of
southwest Montana. The chances of precipitation have been changed
to reflect this. Have generally dropped the mention of
precipitation over the Rocky Mountain Front for the rest of
tonight with the exception have left in a slight chance near
Glacier Park for the rest of this evening. Have decreased sky
cover over the central zones for the rest of this evening in line
with latest satellite imagery and expected trend. Also have
dropped the mention of thunder for the rest of this evening as the
air mass has been generally stabilizing. Blank
&&
.AVIATION...
Updated 0455Z.
Generally VFR conditions will prevail over the region through the
period. However...isolated evening showers/TS will affect far SW MT
this evening...mainly along a line from Butte to White Sulphur
Springs. This precipitation activity should diminish by 10z. Expect
new storms to redevelop after 21z on Monday over Southwest MT. They
will push northward towards Central MT by 00z Tue. Mainly kept VCTS
at the terminals for now on Monday afternoon...as TS activity looks
to be fairly isolated...and confidence is low right now about any
particular terminal being hit by a TS. Brusda
&&
.HYDROLOGY...
A point flood warning remains in effect for the Big Sandy Creek
near Havre. A few showers and thunderstorms are possible Monday
and Tuesday of this week, but they should not impact the river
level there significantly. The level should very gradually
decrease through the early part of the week, but it is expected to
remain above flood stage.
&&
.PREV DISCUSSION...
/ISSUED 555 PM MDT Sun Jun 16 2013/
Tonight through Tuesday night...Central Montana will be underneath a
high pressure ridge tonight and Monday. A low pressure system over
the Eastern Pacific will be approaching the West Coast Monday and
the effects of this system should start to affect the Northern
Rockies by late afternoon. The airmass will still be rather dry and
most convection will likely begin over the mountains and move
northeast. Neither CAPE nor shear is particularly strong, however,
together some severe thunderstorms are possible. South to southeast
low-level flow will strengthen Monday night and should help moisten
lower layers across the central and northern zones...dewpoints
should be rising late Monday night through Tuesday. The upper level
low pressure center to the west will move over the West Coast late
Tuesday. Moist, unsettled southwest flow ahead of this system will
move over western and central Montana. Instability will increase
during the afternoon with CAPE values in excess of 4000 forecasted
across the central zones. Convective temperatures will be rather
high to the east and convection will generally begin to the west
over the Rockies. A cold front will move through the Rockies by
late afternoon and add some lift to the airmass. This front will
bring increased shear into a very unstable environment as it moves
east during the evening. This will be a wet system with periods of
heavy rain and large hail lasting well into the evening.
Wednesday through Sunday...The medium range will be
influenced by southwest flow aloft as a closed upper low will
push into the Pacific Northwest and move slowly north and east
across southern Canada through the period. Southwest flow aloft
ahead of the low on Wednesday will pull moisture across the
eastern and northern portion of the county warning area resulting
in widespread afternoon thunderstorms. CAPE values Wednesday
afternoon approach 4000 J/kg across the eastern Hi-Line,
resulting in the possibility of strong thunderstorms. Scattered
showers and thunderstorms will continue through the week though
models indicate available moisture will slowly decreases allowing
for areal coverage and intensity of these storms will diminish as
the weekend approaches. By Sunday, the upper low moves to western
Saskatchewan and convective activity becomes isolated over the
area. Temperatures will be generally near to slightly below
seasonal averages.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 44 80 52 85 / 0 10 30 30
CTB 43 79 49 82 / 10 20 30 40
HLN 48 82 52 86 / 10 20 30 50
BZN 42 81 46 86 / 20 20 20 40
WEY 36 75 39 78 / 20 20 20 30
DLN 45 81 48 84 / 20 20 30 40
HVR 46 81 53 88 / 0 10 10 10
LWT 45 76 50 83 / 10 10 20 20
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
Flood warning continues for Big Sandy Creek near Havre until
further notice.
&&
$$
SHORT TERM...BLANK
LONG TERM...BRUSDA
AVIATION...BRUSDA
weather.gov/greatfalls
000
FXUS65 KTFX 170323
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
923 PM MDT Sun Jun 16 2013
.UPDATE...
A few showers continue over southwest Montana at mid-evening but
now the main ones are over the northern portion of southwest
Montana whereas earlier they were over the southern portion of
southwest Montana. The chances of precipitation have been changed
to reflect this. Have generally dropped the mention of
precipitation over the Rocky Mountain Front for the rest of
tonight with the exception have left in a slight chance near
Glacier Park for the rest of this evening. Have decreased sky
cover over the central zones for the rest of this evening in line
with latest satellite imagery and expected trend. Also have
dropped the mention of thunder for the rest of this evening as the
air mass has been generally stabilizing. Blank
&&
.AVIATION...
Updated 2355Z.
Generally VFR conditions will prevail over the region through the
period. However...isolated evening showers/TS will affect far SW MT
this evening...mainly south of line from Butte to White Sulphur
Springs. For now...held off on TS in the Bozeman area. This
precipitation activity should diminish by 08z. Expect new storms to
redevelop after 21z on Monday over Southwest MT. They will push
northward towards Central MT by 00z Tue. Brusda
&&
.HYDROLOGY...
A point flood warning remains in effect for the Big Sandy Creek
near Havre. A few showers and thunderstorms are possible Monday
and Tuesday of this week, but they should not impact the river
level there significantly. The level should very gradually
decrease through the early part of the week, but it is expected to
remain above flood stage.
&&
.PREV DISCUSSION...
/ISSUED 555 PM MDT Sun Jun 16 2013/
Tonight through Tuesday night...Central Montana will be underneath a
high pressure ridge tonight and Monday. A low pressure system over
the Eastern Pacific will be approaching the West Coast Monday and
the effects of this system should start to affect the Northern
Rockies by late afternoon. The airmass will still be rather dry and
most convection will likely begin over the mountains and move
northeast. Neither CAPE nor shear is particularly strong, however,
together some severe thunderstorms are possible. South to southeast
low-level flow will strengthen Monday night and should help moisten
lower layers across the central and northern zones...dewpoints
should be rising late Monday night through Tuesday. The upper level
low pressure center to the west will move over the West Coast late
Tuesday. Moist, unsettled southwest flow ahead of this system will
move over western and central Montana. Instability will increase
during the afternoon with CAPE values in excess of 4000 forecasted
across the central zones. Convective temperatures will be rather
high to the east and convection will generally begin to the west
over the Rockies. A cold front will move through the Rockies by
late afternoon and add some lift to the airmass. This front will
bring increased shear into a very unstable environment as it moves
east during the evening. This will be a wet system with periods of
heavy rain and large hail lasting well into the evening.
Wednesday through Sunday...The medium range will be
influenced by southwest flow aloft as a closed upper low will
push into the Pacific Northwest and move slowly north and east
across southern Canada through the period. Southwest flow aloft
ahead of the low on Wednesday will pull moisture across the
eastern and northern portion of the county warning area resulting
in widespread afternoon thunderstorms. CAPE values Wednesday
afternoon approach 4000 J/kg across the eastern Hi-Line,
resulting in the possibility of strong thunderstorms. Scattered
showers and thunderstorms will continue through the week though
models indicate available moisture will slowly decreases allowing
for areal coverage and intensity of these storms will diminish as
the weekend approaches. By Sunday, the upper low moves to western
Saskatchewan and convective activity becomes isolated over the
area. Temperatures will be generally near to slightly below
seasonal averages.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 44 80 52 85 / 0 10 30 30
CTB 43 79 49 82 / 10 20 30 40
HLN 48 82 52 86 / 10 20 30 50
BZN 42 81 46 86 / 20 20 20 40
WEY 36 75 39 78 / 20 20 20 30
DLN 45 81 48 84 / 20 20 30 40
HVR 46 81 53 88 / 0 10 10 10
LWT 45 76 50 83 / 10 10 20 20
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
Flood warning continues for Big Sandy Creek near Havre until
further notice.
&&
$$
SHORT TERM...BLANK
LONG TERM...BRUSDA
AVIATION...BRUSDA
weather.gov/greatfalls
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