482
FXUS65 KTFX 271525
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
825 AM MST MON JAN 27 2025
KEY MESSAGES
- BREEZY WESTERLY WINDS WILL WARM TEMPERATURES ABOVE NORMAL
ACROSS MUCH OF NORTH CENTRAL AND CENTRAL MONTANA THIS WEEK,
POSSIBLY CAUSING PATCHY BLOWING SNOW TODAY.
- TEMPERATURES WILL BE SLOWER TO WARM IN THE VALLEYS OF CENTRAL
AND SOUTHWEST MONTANA.
- WINDS MAY BECOME STRONG ON THE ROCKY MOUNTAIN FRONT ON
WEDNESDAY.
- COLDER WITH INCREASED CHANCES FOR SNOW THIS WEEKEND AND AT
LEAST INTO EARLY NEXT WEEK.
UPDATE
SATELLITE IMAGERY THIS MORNING SHOWS MAINLY CLEAR SKIES WITH JUST
SOME HIGH CLOUDS SPILLING SOUTH ACROSS THE AREA IN A DRY
NORTHERLY FLOW ALOFT DOWNSTREAM OF AN UPPER LEVEL RIDGE CENTERED
WEST OF THE REGION. VALLEY COLD POOLS/TEMPERATURE INVERSIONS
CONTINUE TO AFFECT SW MT WHERE VALLEY TEMPERATURES ARE STARTING
OFF IN THE SINGLE DIGITS THIS MORNING WHILE AREAS ON THE PLAINS
ARE ALREADY WELL INTO THE 20S. AFTERNOON TEMPERATURES ARE ON TRACK
TO REACH SEASONAL LEVELS (30S) ON THE PLAINS WHILE MUCH COOLER
TEMPS LINGER IN SW MT. PREVIOUS FORECAST HANDLES THIS WELL WITH
NO UPDATES NEEDED THIS MORNING. HOENISCH
DISCUSSION
/ISSUED 429 AM MST MON JAN 27 2025/
- METEOROLOGICAL OVERVIEW:
TODAY THROUGH THURSDAY...
A LOW PRESSURE CENTER OVER THE SOUTHWESTERN UNITED STATES WITH A
HIGH PRESSURE RIDGE OVER THE PACIFIC NORTHWEST INTO MONTANA WILL
CONTINUE THE STAGNANT REX BLOCK PATTERN OVER THE FORECAST AREA
THROUGH AT LEAST THURSDAY. AS A RESULT, DRY CONDITIONS ARE
FORECAST TO CONTINUE THROUGH THIS PERIOD. THE NORTHWEST FLOW
ALOFT OVER NORTH CENTRAL AND CENTRAL MONTANA WILL KEEP WINDS
BREEZY OVER THE PLAINS, CAUSING TEMPERATURES TO REMAIN ABOVE
SEASONAL AVERAGES THERE. THE STRONGEST WINDS ARE FORECAST TO
OCCUR ON WEDNESDAY DUE TO MID- LEVEL WIND ENHANCEMENT FROM A
PASSING DISTURBANCE. HOWEVER, THE SUBSIDENCE FROM THE RIDGING,
WHILE KEEPING THE AREA DRY, WILL HELP REINFORCE TEMPERATURE
INVERSIONS IN THE VALLEYS OF CENTRAL AND SOUTHWEST MONTANA, WHICH
WILL KEEP TEMPERATURES BELOW NORMAL THERE OVER THE NEXT FEW DAYS
AND KEEP WINDS LIGHT.
FRIDAY THROUGH NEXT MONDAY...
THE LOW PRESSURE CENTER IS FORECAST TO MOVE EAST INTO THE
SOUTHERN PLAINS ON FRIDAY, WHICH WILL HELP SHIFT THE AXIS OF THE
HIGH PRESSURE RIDGE EAST INTO THE NORTHERN PLAINS AND PUT MONTANA
UNDER MORE OF A SOUTHWESTERLY FLOW ALOFT AHEAD OF AN APPROACHING
LARGE PACIFIC LOW PRESSURE TROUGH. THIS SHOULD HELP MIX WINDS
DOWN INTO THE VALLEYS OF SOUTHWEST AND CENTRAL MONTANA, ALLOWING
TEMPERATURES TO WARM UP CLOSER TO NORMAL. HOWEVER, A SHORTWAVE
TROUGH IS FORECAST TO EJECT FROM THE MAIN TROUGH AND MOVE ACROSS
MONTANA ON SATURDAY, BRINGING AN INCREASED CHANCE FOR SNOW TO THE
FORECAST AREA, POSSIBLY MIXING WITH RAIN OVER THE PLAINS. THE
SHORTWAVE PASSAGE WILL ALSO DRAG A COLD FRONT SOUTH OVER THE
AREA, BRINGING MUCH COLDER TEMPERATURES TO MUCH OF NORTH CENTRAL
AND CENTRAL MONTANA, AND CONTINUING PERIODS OF LIGHT TO AT TIMES
MODERATE SNOW OVER MUCH OF THE AREA. THIS COLDER AIR WILL BE
SLOWER TO MOVE INTO SOUTHWEST MONTANA, REACHING THERE BY MID-
WEEK.
- FORECAST CONFIDENCE & SCENARIOS:
TEMPERATURES THROUGH THURSDAY IN THE VALLEYS...
THE MOST UNCERTAINTY IS REGARDING THE TEMPERATURES IN THE VALLEYS.
HAVE BASED THE TEMPERATURE FORECAST ON THE TREND OF TEMPERATURES
FROM YESTERDAY (AS COMPARED TO THOSE OVER THE MORE BREEZY PLAINS)
AND BLENDED IN SOME OF THE COLDER MODEL FORECASTS TO MAKE WARMING
MORE GRADUAL THERE, ESPECIALLY IN THE STEEPER VALLEY AREAS WHERE
COLD AIR IS MORE DIFFICULT TO SCOUR OUT. CONFIDENCE IS LOW IN THE
EXACT SPEED AND TIMING OF THE WARM UP, WHICH MAY LEAD TO A LONGER
PERIOD OF COOLER VALLEY TEMPERATURES.
WINDS THROUGH THURSDAY OVER THE PLAINS...
CONFIDENCE IS MODERATE TO HIGH THAT WIND STRENGTH WILL SLIGHTLY
OVER-PERFORM THE NBM MODEL, BASED UPON RECENT STRONG WIND
OCCURRENCES. HAVE THEREFORE BLENDED THE NBM WITH THE 90TH
PERCENTILE WINDS OF THE NBM TO INCREASE THEM, WHICH HAS DONE A
BETTER JOB OF REFLECTING THE RESULTING WINDS. THIS STILL KEPT WIND
GUSTS OVER MUCH OF THE PLAINS UNDER HIGH WIND CRITERIA. HOWEVER,
THE FORECAST FOR THE ROCKY MOUNTAIN FRONT AND PLAINS EAST TO CUT
BANK ON WEDNESDAY HAS WINDS AT LEAST APPROACHING THAT CRITERIA.
THE LATEST PROBABILISTIC GUIDANCE ONLY GIVES A 30 TO 50 PERCENT
PROBABILITY THAT THESE AREAS WILL EXCEED HIGH WIND CRITERIA, SO
WILL HOLD OFF ON A HIGH WIND WATCH FOR NOW.
COLD AND SNOW THIS WEEKEND INTO EARLY NEXT WEEK...
ENSEMBLE FORECAST CLUSTER GUIDANCE MAINTAINS A 60/40 PERCENT
SPLIT REGARDING WHETHER TROUGHING OR RIDGING, RESPECTIVELY, WILL
DOMINATE THROUGH THIS PERIOD, SO CONFIDENCE IN MODERATE IN LEANING
TOWARD THE COOLER AND SNOWIER SOLUTION FROM TROUGHING. GIVEN THIS,
THE NBM GIVES A 50+ PERCENT PROBABILITY THAT HIGH TEMPERATURES
WILL NOT REACH 10 DEGREES F OVER NORTH CENTRAL AND CENTRAL MONTANA
ON SUNDAY, AND A SIMILAR PROBABILITY OF HIGHS BELOW ZERO FOR
MONDAY. THERE IS A 50+ PERCENT PROBABILITY OF LOWS BELOW ZERO ON
THE HI-LINE SATURDAY NIGHT, WHICH SPREAD SOUTH INTO THE HELENA
AREA FOR SUNDAY NIGHT WITH A SIMILAR PROBABILITY OF LOWS BELOW 10
BELOW ZERO ON THE HI-LINE. 72-HOUR SNOW GUIDANCE GIVES A 20 TO 40
PERCENT PROBABILITY OF 4+ INCHES OF SNOW AT MOST LOWER ELEVATIONS,
AND A GREATER THAN 50 PERCENT PROBABILITY OF 8+ INCHES IN MOST
MOUNTAIN RANGES. THERE IS STILL QUITE A BIT OF UNCERTAINTY WHETHER
THIS WINTER WEATHER EVENT WILL REACH WINTER STORM OR EXTREME COLD
CRITERIA AT THIS TIME, SO THE SITUATION WILL CONTINUE TO BE
EVALUATED THIS WEEK. -COULSTON
AVIATION
27/12Z TAF PERIOD
VFR CONDITIONS ARE EXPECTED TO PREVAIL ACROSS THE CWA THROUGH THE
PERIOD. DO EXPECT BREEZY SOUTHWEST WINDS OVER NORTH CENTRAL MT
THROUGH TONIGHT THOUGH. BRUSDA
REFER TO WEATHER.GOV/ZLC FOR MORE DETAILED REGIONAL AVIATION
WEATHER AND HAZARD INFORMATION.
PRELIMINARY POINT TEMPS/POPS
GTF 37 19 38 21 / 0 0 0 0
CTB 39 19 42 21 / 0 0 0 0
HLN 20 3 26 9 / 0 0 0 0
BZN 19 -2 25 4 / 0 0 0 0
WYS 16 -18 24 -15 / 0 0 0 0
DLN 23 6 26 10 / 0 0 0 0
HVR 36 17 39 16 / 0 0 0 0
LWT 38 19 41 19 / 0 0 0 0
TFX WATCHES/WARNINGS/ADVISORIES
NONE.
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