000
FXUS65 KTFX 061135
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
435 AM MST TUE JAN 6 2009
...UPDATE TO AVIATION...
.DISCUSSION...
TODAY THROUGH THURSDAY...STRONG/MOIST NW FLOW ALOFT WILL REMAIN
OVER THE REGION THROUGH THE MIDDLE OF THIS WEEK WITH SEVERAL
EMBEDDED DISTURBANCES TO IMPACT THE REGION. AN UPPER LEVEL JET
MAXIMUM MOVES SE INTO THE NORTHERN ROCKIES TODAY WITH MOISTURE
INCREASING ALONG AND WEST OF THE CONTINENTAL DIVIDE THROUGH THE
DAY...SPREADING INTO THE SW MT MOUNTAINS THIS AFTERNOON. LATE THIS
AFTERNOON THROUGH TONIGHT...AS THE UPPER LEVEL JET AND MID LEVEL
DISTURBANCE PROGRESS OVERHEAD...A NW TO SE ORIENTED SURFACE
TROUGH OF LOW PRESSURE DEVELOPS AND SHIFTS EAST ACROSS CENTRAL MT.
AN AREA OF SNOW WILL DEVELOP ALONG AND NE NE OF THE SURFACE
TROUGH BY THIS EVENING AND SLOWLY MOVE EAST OVERNIGHT. BEST CHANCE
OF PRECIPITATION WITH THIS FEATURE WILL BE TO THE EAST OF A LINE
FROM KCTB TO KGTF TO KBZN. EXPECT SIGNIFICANT ACCUMULATIONS WITH
THIS FEATURE OVER NORTHERN PORTIONS OF THE CONTINENTAL DIVIDE AND
OVER THE MTNS OF SW MT WHERE 6-12 INCHES OF NEW SNOW IS EXPECTED
BY WEDNESDAY MORNING. OVER THE PLAINS/LOWER ELEVATIONS OF THE
FORECAST AREA...SNOW AMOUNTS THROUGH WEDNESDAY MORNING WILL
GENERALLY BE LESS THAN THREE INCHES...HOWEVER THE SITUATION BEARS
WATCHING AS MODELS HAVE BEEN ON AN INCREASING TREND WITH QPF
AMOUNTS OVER THE LAST FEW MODEL RUNS...ESPECIALLY OVER JUDITH
BASIN AND FERGUS COUNTIES. WINTER WEATHER HIGHLIGHTS WILL BE
ISSUED FOR THE HIGHER ELEVATIONS OF GALLATIN AND MADISON
COUNTY(INCLUDING WEST YELLOWSTONE) FOR THIS AFTERNOON THROUGH
THURSDAY MORNING. A WINTER STORM WARNING WILL ALSO TAKE EFFECT
THIS AFTERNOON FOR THE ROCKY MTN FRONT MOUNTAINS(ABOVE 5000FT).
EXPECT SNOW TO CONTINUE ALONG THE ROCKY MTN FRONT THROUGH THURSDAY
AS THE MOIST WNW FLOW ALOFT CONTINUES TO BRING STEADY OROGRAPHIC
PRECIP TO THOSE LOCATIONS. IN ADDITION TO THE SNOW...STRONG WINDS
WILL ALSO CREATE HAZARDOUS CONDITIONS IN THE MTNS ALONG THE ROCKY
MTN FRONT AND ESPECIALLY OVER MARIAS PASS THROUGH THE NEXT 48 HRS.
THE SURFACE TROUGH LIFTS NE ACROSS NORTH CENTRAL MT ON WEDNESDAY
AND SNOW MAY END NS SOME AREAS AS LIGHT RAIN AS MILDER
TEMPERATURES AND WINDY CONDITIONS DEVELOP BEHIND THE TROUGH. VERY
WINDY CONDITIONS WILL DEVELOP FIRST ALONG THE ROCKY MTN FRONT AND
ADJACENT PLAINS TONIGHT...THEN SPREAD EAST ONTO WESTERN AND
SOUTHWEST PORTIONS OF NORTH CENTRAL MT ON WEDNESDAY. HAVE UPGRADED
THE HIGH WIND WATCH FOR THE ROCKY MTN FRONT AND EASTERN GLACIER
COUNTY TO A WARNING AND WILL INCLUDE A HIGH WIND WATCH FOR AREAS
TO THE EAST FOR WEDNESDAY THROUGH WEDNESDAY EVENING. SURFACE
PRESSURE GRADIENT RELAXES SOME ACROSS THE FORECAST AREA ON
THURSDAY WITH DOWNSLOPE WINDS KEEPING TEMPS MILD EAST OF THE
ROCKIES. STEADY FLOW OF MOISTURE INTO NW MT WILL KEEP SNOW GOING
OVER THE WESTERN MTNS AND WINTER WEATHER HIGHLIGHTS MAY NEED TO BE
CONTINUED FOR THE HIGHER ELEVATIONS OF THE ROCKY MTN FRONT.
HOENISCH
THURSDAY NIGHT THROUGH TUESDAY NIGHT...MODELS CONTINUE TO BRING A
CLOSED SURFACE LOW THROUGH SOUTHERN ALBERTA INTO EASTERN MONTANA ON
THURSDAY...THEN BRING A COLD FRONT SOUTH OUT OF ALBERTA DURING THE
OVERNIGHT HOURS. MODELS HAVE BACKED OFF A BIT ON QPF AMOUNTS...BUT
WOULD EXPECT THAT SNOW SHOULD STILL BECOME LIKELY ACROSS PORTIONS OF
NORTH CENTRAL MONTANA AS THE COLD FRONT SLIPS SOUTH THURSDAY
EVENING...WITH AREAS OF BLOWING SNOW EXPECTED AS GUSTY NORTHERLY
WINDS SET UP BEHIND THE FRONT. THE COOL DOWN WILL BE SHORT LIVED AS
THE UPPER LEVEL FLOW RETURNS TO NORTHWEST FLOW ALOFT WHEN ANOTHER
BROAD RIDGE SETS UP IN THE EASTERN PACIFIC FOR THE WEEKEND. MODELS
REMAIN IN DECENT AGREEMENT KEEPING A SURFACE LOW PRESSURE TROUGH IN
ALBERTA AND SASKATCHEWAN FOR GUSTY WESTERLY WINDS ACROSS MY FORECAST
AREA WITH TEMPERATURES EXPECTED TO BE NEAR OR ABOVE SEASONAL
AVERAGES AND THE CHANCE OF PRECIPITATION NEAR OR BELOW CLIMATOLOGY.
MODEL SOLUTIONS DIVERGE EARLY NEXT WEEK BUT IT APPEARS PROBABLY THAT
ANOTHER ARCTIC AIRMASS WILL MOVE SOUTH OUT OF CANADA. QUESTION
APPEARS TO BE WHETHER IT MOVES INTO MONTANA...OR COMES DOWN FARTHER
EAST IN THE DAKOTAS. FOR NOW WILL GO WITH A COMPROMISE SOLUTION THAT
COOLS OFF TEMPERATURES SOMEWHAT...AND INCREASES THE CHANCE OF
PRECIPITATION. WOULD EXPECT THAT IF THE ARCTIC AIRMASS DOES COME IN
FARTHER TO THE WEST TEMPERATURES WOULD NEED TO BE DROPPED
SIGNIFICANTLY MORE. MPJ
&&
.AVIATION...
MOIST NORTHWEST FLOW ALOFT WILL CONTINUE TODAY THROUGH WEDNESDAY
MORNING. LOW AND MID LEVEL CLOUD COVER WILL INCREASE ACROSS THE
REGION AFTER 18Z TODAY WITH ISOLATED TO SCATTERED SNOW SHOWERS
POSSIBLY AFFECTING THE WESTERN FORECAST TERMINALS WITH BRIEF
PERIODS OF MVFR CONDITIONS. AFTER 00Z WEDNESDAY LIGHT SNOW IS
EXPECTED TO BECOME WIDESPREAD IN SOUTHWEST MONTANA...AS WELL AS
SOUTHERN AND EASTERN PORTIONS OF NORTH CENTRAL MONTANA. MVFR AND
AREAS OF IFR CONDITIONS WILL PREVAIL IN THIS REGION WITH
CONDITIONS IMPROVING FROM THE WEST AFTER 06Z. MPJ
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 37 31 47 35 / 20 60 20 10
CTB 35 28 44 33 / 10 20 10 10
HLN 38 35 48 33 / 20 40 10 10
BZN 37 32 48 32 / 30 60 30 20
WEY 22 18 33 23 / 70 90 70 60
DLN 34 30 45 30 / 20 30 20 10
HVR 28 21 38 24 / 20 60 60 20
LWT 34 26 45 30 / 30 80 70 20
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WATCH FROM LATE TONIGHT THROUGH WEDNESDAY EVENING FOR
MTZ012-046-049-050.
HIGH WIND WARNING FROM 8 PM THIS EVENING TO 5 AM MST THURSDAY
FOR MTZ009-010-048.
WINTER STORM WARNING FROM NOON TODAY TO NOON MST THURSDAY FOR
MTZ009-048.
WINTER STORM WARNING FROM NOON TODAY TO NOON MST WEDNESDAY FOR
MTZ015-055.
&&
$$
SHORT TERM...HOENISCH
LONG TERM...MPJ
AVIATION...MPJ
WEATHER.GOV/GREATFALLS
