FXUS65 KTFX 272320
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
420 PM MST FRI NOV 27 2009
.DISCUSSION...
SHORT TERM...
TONIGHT THROUGH SATURDAY NIGHT...TRICKY FORECAST FOR TONIGHT WITH
REGARDS TO AMOUNT OF PRECIPITATION AS SHORTWAVE TROUGH MOVES OVER
CENTRAL AND SOUTHWEST MONTANA. BANDS OF PACIFIC MOISTURE WILL
CONTINUE TO MOVE OVER THE REGION THIS EVENING AND
TONIGHT...HOWEVER MOST OF THE MOISTURE SEEMS TO BE CONCENTRATED
OVER THE MID TO UPPER LEVELS WITH LIMITED LOW-LEVEL MOISTURE
PRESENT. OROGRAPHICALLY ENHANCED LIFT OVER THE MOUNTAINS IN
ADDITION TO A FAST-MOVING UPPER-LEVEL SHORTWAVE AND JET MAX WILL
ALLOW FOR LIGHT SNOW TO DEVELOP OVERNIGHT WITH 2 TO 4 INCHES OF
SNOW POSSIBLE IN THE HIGHER ELEVATIONS OF SOUTHWEST
MONTANA...INCLUDING THE MADISON..GALLATIN AND BRIDGER MTN RANGES.
IN THE VALLEYS...RAIN AND SNOW SHOWERS ARE POSSIBLE THIS EVENING
THEN ALL SNOW SHOWERS AS COOLER AIR MOVES IN...HOWEVER LITTLE TO
NO SNOW ACCUMULATION IS EXPECTED. ACROSS CENTRAL AND NORTH-CENTRAL
MONTANA...A CHANCE OF RAIN AND SNOW SHOWERS IS POSSIBLE BEFORE
MIDNIGHT IN THE PLAINS WITH SNOW SHOWERS ALONG THE SOUTHERN ROCKY
MOUNTAIN FRONT..LITTLE AND BIG BELT MOUNTAINS WITH LESS THAN 3
INCHES OF SNOW ACCUMULATION. THUS...WINTER HIGHLIGHTS SHOULD NOT
BE NECESSARY. ON SATURDAY...AN UPPER-LEVEL RIDGE WILL BUILD OVER
THE REGION WITH COOL NORTHWEST FLOW PERSISTING AND ONLY A SLIGHT
CHANCE OF SHOWERS ALONG THE ROCKY MOUNTAIN FRONT. HIGH
TEMPERATURES WILL BE AROUND SEASONAL AVERAGES. MLS
LONG TERM...
SUNDAY AND MONDAY...
RIDGING WORKS EAST INTO THE TREASURE STATE SUNDAY...MODEST WNW FLOW
ACROSS THE REGION AS THE UPPER LEVEL JET IS WELL TO THE NORTH ACROSS
CENTRAL BRITISH COLUMBIA INTO THE PRAIRIE PROVINCES. MOSTLY DRY
ACROSS THE REGION...THOUGH A FEW MOUNTAIN SNOW SHOWERS MAY BE
POSSIBLE ALONG AREAS MORE PERPENDICULAR TO THE FLOW DUE TO UPSLOPE.
TEMPE SHOULD END UP JUST A BIT ABOVE NORMAL ACROSS THE REGION.
FLOW BECOMES MORE WESTERLY AND STARTS TO INCREASE ON MONDAY. GUSTY
WINDS WILL BE POSSIBLE BY AFTERNOON...WITH SOME STRONG GUSTS
POSSIBLE BY MON 21Z-TUE 00Z AS H700 WINDS REACH 50-60 KTS...HEADLINE
MAY BE POSSIBLE FOR THESE STRONG GUSTY WINDS WITH THE MOST LIKELY
AREA BEING THE NORTHERN ROCKY MTN FRONT AND ADJACENT AREAS.
DOWNSLOPE WINDS WILL ALLOW FOR AFTN TEMPS TO REACH LEVEL WELL ABOVE
NORMAL BY 10-15 DEGREES...LESSER EFFECT ACROSS SW MONTANA.
TUESDAY THROUGH WEDNESDAY...
VERY LITTLE HAS CHANGED IN TERMS TO THIS TIMEFRAME OVER THE LAST
36-48 HOURS. GFS IS STILL THE OUTLIER WITH THE NEXT PRECIP
POSSIBILITY FOR TUESDAY. EURO/UKMET/CANADIAN/ AND GFS ENSEMBLE MEAN
STILL PRODUCING PRECIP ACROSS THE REGION DURING THE DAY. SOME
UNCERTAINTY STILL EXISTS...BUT WITH CONSISTENT MODEL RUNS THE LAST
FEW DAYS THEY ARE NOT TOO GREAT. ANY SNOWFALL AMOUNTS WOULD BE LIGHT
AS OF CURRENT THINKING. PRECIP IS ASSOCIATED WITH UPPER LEVEL TROUGH
AND JET PUSHING ACROSS THE REGION...THESE FEATURES MOVE THROUGH
FAIRLY QUICKLY WITH THE AREA DRYING OUT TUESDAY EVENING. WINDS RELAX
SOME DURING THE DAY TUESDAY...AND THE FLOW BECOMES NORTHERLY
USHERING COLDER AIR INTO BIG SKY COUNTRY. DRY NORTHERLY FLOW AND
BELOW NORMAL TEMPS WILL CONTINUE WEDNESDAY AS SFC HIGH MAY DROP
SOUTH FROM CANADA. --SCHOTT
&&
.AVIATION...
UPDATED 2318Z.
A WEAK UPPER LEVEL LOW PRESSURE TROF WILL MOVE THROUGH THE REGION
THIS EVENING. AN ASSOCIATED COLD FRONT WILL KEEP LOW CLOUDS ACROSS
THE AREA ALONG WITH A CHANCE OF RAIN AND SNOW. HIGH PRESSURE WILL
BEGIN TO BUILD AGAIN BEHIND THE TROF AND THE AIRMASS WILL DRY ON
SATURDAY. LOCAL MVFR CONDITIONS DUE TO VSBY AND CIGS ARE POSSIBLE
ACROSS THE NORTH CENTRAL AND SOUTHWEST MONTANA...AND IFR CONDITIONS
ARE POSSIBLE OVER THE WESTERN MOUNTAINS. VFR CONDITIONS ARE EXPECTED
ACROSS THE REGION BY MID MORNING SATURDAY.
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF 25 40 26 44 / 30 10 10 0
CTB 23 39 23 44 / 40 0 10 0
HLN 26 40 22 43 / 40 10 20 10
BZN 22 35 15 35 / 50 20 10 0
WEY 5 28 3 26 / 60 40 20 10
DLN 16 32 15 34 / 50 10 10 0
HVR 23 42 21 46 / 30 0 10 0
LWT 24 39 21 41 / 40 10 10 0
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
WEATHER.GOV/GREATFALLS
