FXUS65 KTFX 270538
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1038 PM MST THU NOV 26 2009
.UPDATE...
ANOTHER QUIET NIGHT WITH NOT TOO MUCH GOING ON ACROSS THE AREA. AN
APPROACHING SHORTWAVE AND ASSOCIATED SHOWERS ARE JUST BEGINNING TO
MAKE THEIR WAY TO THE WESTERN SIDE OF THE CONTINENTAL DIVIDE AND
WILL CONTINUE TO DO SO THROUGH THE NIGHT. EXPECT SCATTERED SHOWERS
TO MAKE IT ACROSS THE DIVIDE EARLY TOMORROW WITH SOME PRECIPITATION
FALLING MAINLY ALONG HIGHER TERRAIN. EXPECTING SHOWERS TO START
OUT AS RAIN AND CHANGE TO SNOW AS COOLER AIR BEHIND THE TROUGH
MOVES IN. NOT EXPECTING MUCH IN THE WAY OF ACCUMULATION THOUGH.
UPPED SOME TEMPS THIS EVENING WITH CLOUD COVER BEING GREATER THAN
ORIGINALLY THOUGHT. TWEAKED POPS WITH THE APPROACHING TROUGH TO
BETTER ADJUST TO CURRENT MODEL TRENDS. ONLY OTHER GRID EDITS WERE
COSMETIC IN NATURE.
&&
.AVIATION...
UPDATED 0533Z.
AN UPPER LEVEL HIGH PRESSURE RIDGE WILL MOVE EAST OF MONTANA WHILE A
LOW PRESSURE TROF TO THE WEST MOVES ON SHORE. THIS WILL CAUSE
INCREASING CLOUD COVER THROUGH THE NIGHT. CLOUDS WILL CONTINUE TO
LOWER THROUGH FRIDAY WITH A CHANCE OF PRECIPITATION DEVELOPING OVER
THE WESTERN MOUNTAINS BY LATE FRIDAY AFTERNOON. SCATTERED SHOWERS
WILL SPREAD EAST OVER CENTRAL AND SOUTHWEST MONTANA FRIDAY EVENING.
MOST PRECIPITATION WILL BE RAIN AT LOWER ELEVATIONS AND SNOW IN THE
MOUNTAINS. MVFR CIGS ARE EXPECTED BY FRIDAY OVER THE
MOUNTAINS...ELSEWHERE VFR CONDITIONS SHOULD PREVAIL EXCEPT NEAR SNOW
SHOWERS DURING THE NEXT 24 HOURS.
&&
.PREV DISCUSSION...
/ISSUED 401 PM MST THU NOV 26 2009/
SHORT TERM...
TONIGHT
CHINOOK ARCH WILL PERSIST ACROSS NORTH-CENTRAL AND
CENTRAL MONTANA THROUGH THIS EVENING WHICH WILL RESULT IN PARTLY
TO MOSTLY CLOUDY SKIES. UPPER-LEVEL RIDGE CONTINUES TO BREAK DOWN
WITH WEAK EMBEDDED SHORTWAVES AND LIMITED MOISTURE AS WEST-
SOUTHWESTERLY FLOW DEVELOPS OVERNIGHT.
FRIDAY AND FRIDAY NIGHT
NEXT SHORTWAVE TROUGH WILL MOVE INTO THE PACIFIC NORTHWEST ON
FRIDAY AND MODELS SEEM TO BE IN BETTER AGREEMENT IN TERMS OF
PLACEMENT AND INTENSITY. UPPER-LEVEL TROUGH WILL SPLIT WITH
SOUTHERN PORTION MOVING INTO NORTHERN CALIFORNIA AND THE NORTHERN
BRANCH WILL MOVE OVER IDAHO AND MONTANA. STILL SOME MODEL
DIFFERENCES WITH REGARDS TO AMOUNT OF MOISTURE...HOWEVER CURRENT
THINKING IS THAT MAJORITY OF PACIFIC MOISTURE WILL BE WRAPPED INTO
THE SOUTHERN BRANCH OVER CALIFORNIA LEAVING LIMITED MOISTURE AND
ENERGY OVER NORTH-CENTRAL..CENTRAL AND SOUTHWEST MONTANA. A WEAK
COLD FRONT IS ALSO PROGGED TO MOVE THROUGH THE REGION WHICH WILL
RESULT IN A COOLER AIRMASS OVER THE AREA BY SATURDAY. BEST LIFT
WILL STILL BE OVER THE MOUNTAINS...PARTICULARLY ALONG THE ROCKY
MOUNTAIN FRONT AND SOUTHWEST MONTANA MOUNTAINS WHERE A FEW INCHES
OF SNOW IS POSSIBLE THROUGH SATURDAY MORNING. AT THIS
TIME...WINTER HIGHLIGHTS WILL NOT BE NECESSARY BUT WILL CONTINUE
TO MONITOR. IN THE VALLEYS AND PLAINS...PRECIPITATION WILL
PROGRESS FROM WEST TO EAST STARTING FRIDAY MORNING WITH MAINLY
RAIN SHOWERS DURING THE DAY POSSIBLY MIXING WITH SNOW SHOWERS BY LATE
FRIDAY AND CHANGING TO ALL SNOW SHOWERS FRIDAY NIGHT AS A COOLER
AIRMASS MOVES OVER THE AREA. HIGH TEMPERATURES ON FRIDAY WILL
REMAIN 15 TO 20 DEGREES ABOVE AVERAGE BEFORE THE COOLER AIR
ARRIVES. MLS
LONG TERM...
SATURDAY AND SUNDAY
COOLER AIR WILL HAVE OVERSPREAD THE REGION BY SATURDAY MORNING WITH
MODEST NW FLOW ACROSS THE TREASURE STATE. SHORTWAVE PUSHES THROUGH
THE REGION DURING THE AFTN/EVENING TIMEFRAME...LAPSE RATES INCREASE
TO AROUND 7.5-8 C/KM...AND THE REGION SITS IN THE LEFT EXIT REGION
OF THE JET...ALL ALLOWING FOR SOME SNOW SHOWERS BUT MAINLY ACROSS
THE ROCKY MTN FRONT AND ACROSS SW MONTANA. SFC HIGH PRESSURE AND
UPPER LEVEL RIDING WORKS INTO THE AREA SUNDAY MORNING INTO THE
AFTERNOON WITH COOL NORTHERLY FLOW CONTINUING...DRY CONDITIONS
SHOULD PREVAIL THROUGH THE DAY. MORE SEASONAL TEMPS ARE LIKELY FOR
SATURDAY...WITH SUNDAY JUST SLIGHTLY WARMER THAN AVERAGE.
MONDAY THROUGH THURSDAY..
GFS MODEL IS HAVING SIGNIFICANT ISSUES AND HAS DEVIATED DRAMATICALLY
FROM PREVIOUS RUNS...EURO/UKMET/CANADIAN AND EVEN THE GFS ENSEMBLE
MEAN HAVE NOT MADE SUCH A CHANGE SO HAVE CONTINUED THE THINKING OF A
DECENT PRECIP PRODUCER TUESDAY AND COLDER TEMPS COMING LATE IN THE
FORECAST PERIOD. SOME UNCERTAINTY AS TYPHOON NIDA IN THE WESTERN
PACIFIC WILL IMPACT THE WEATHER PATTERNS IN A SIGNIFICANT WAY ONCE
IT STARTS TO GO EXTRA-TROPICAL IN THE NEXT FEW DAYS...USUALLY THIS
CREATES A VERY AMPLIFIED PATTERN ACROSS THE EASTERN PACIFIC AND OVER
NORTH AMERICA.
CURRENT THINKING GOES AS FOLLOWS...RIDGING...DRY AND MUCH ABOVE
NORMAL TEMPS ARE LIKELY FOR MONDAY. AS THE NEXT SYSTEM HEADS TOWARDS
BIG SKY COUNTRY MONDAY NIGHT VERY GUSTY WINDS MAY BE POSSIBLE ACROSS
MUCH OF THE REGION...HEADLINES MAY BE NECESSARY ACROSS PORTIONS OF
THE REGION. A FAST MOVING SHORTWAVE DROPS THROUGH THE REGION
TUESDAY...DECENT CHANCES FOR AN AREA WIDE SNOWFALL. AS STRONG
SURFACE HIGH PRESSURE DROPS SOUTH INTO THE REGION TUESDAY NIGHT INTO
WEDNESDAY MUCH COLDER AIR MAY INVADE THE REGION...AND MAY HANG
AROUND FOR AWHILE. SOME SCTD SNOW SHOWERS MAY LINGER IN THE HIGHER
ELEVATIONS ON WEDNESDAY BEFORE DRYING OUT BY THURSDAY. --SCHOTT
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 37 50 25 36 / 0 20 20 10
CTB 32 44 23 35 / 20 40 30 10
HLN 29 48 26 37 / 0 30 30 20
BZN 22 45 22 31 / 0 20 40 20
WEY 15 35 15 26 / 0 30 50 40
DLN 24 43 20 31 / 0 20 30 10
HVR 29 51 23 38 / 0 20 20 10
LWT 31 51 24 34 / 0 10 30 10
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...GUSTAFSON
LONG TERM...SCHOTT
AVIATION...ZELZER
WEATHER.GOV/GREATFALLS
