006
FXUS65 KTFX 181920
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
120 PM MDT SUN OCT 18 2026
KEY MESSAGES
- CONDITIONS REMAIN DRY THROUGH MIDWEEK FOR MOST OF THE REGION,
WITH LOW END CHANCES FOR SHOWERS IN SOUTHWEST MT TUESDAY AND
WEDNESDAY.
- BETTER CHANCES FOR PRECIPITATION ACROSS THE REGION COMES LATE
THURSDAY INTO FRIDAY.
DISCUSSION
- METEOROLOGICAL OVERVIEW:
WEAK ZONAL FLOW ALOFT CONTINUES TODAY, BRINGING BENIGN CONDITIONS
TO THE REGION WITH TEMPERATURES NEAR NORMAL. ZONAL FLOW
TRANSITIONS TO INCREASING SOUTHWEST FLOW HEADING INTO THE FIRST
HALF OF THE WEEK AS THE NEXT INCOMING TROUGH COMES ONSHORE TO THE
WESTERN U.S. THIS NEXT TROUGH SPLITS OFF INTO A CUT OFF LOW DOWN
IN CA/GREAT BASIN REGION, WHICH INCREASES WARM, SOUTHWEST FLOW
ALOFT AND MOISTURE. AS A RESULT, TEMPERATURES TEETER TO NEAR TO
ABOVE NORMAL THROUGH THURSDAY. THE INCREASED MOISTURE ALSO BRINGS
LOW END CHANCES FOR SHOWERS IN SOUTHWEST MT, PARTICULARLY NEAR
THE ID BORDER TUESDAY AND WEDNESDAY.
BETTER FORCING AND MOISTURE ALONG THIS CUTOFF SYSTEM ARRIVES LATE
THURSDAY INTO FRIDAY. AT THE SAME TIME, ANOTHER SHORTWAVE TROUGH
DIPS DOWN FROM CANADA AND INTO MT. THESE TWO SYSTEMS INTERACT AND
EVENTUALLY MERGE INTO EACH OTHER FRIDAY, CREATING A BROAD WAVE.
THIS HELPS BRING BETTER CHANCES FOR PRECIPITATION ACROSS THE
REGION. A COLD FRONTAL PASSAGE FRIDAY ALSO HELP LOWER TEMPERATURES
TO BELOW NORMAL FOR THE WEEKEND. SNOW LEVELS ALSO LOWER BEHIND
THE FRONT FOR LIGHT MOUNTAIN SNOW. THIS TROUGH ALSO LOOKS TO BRING
BREEZY WINDS TO NORTH-CENTRAL MT FRIDAY. ENSEMBLES HINT BEHIND
THIS SYSTEM ANOTHER INCOMING TROUGH MOVING ONSHORE AT THE
BEGINNING OF NEXT WEEK, THOUGH MODELS GREATLY DIVERGE IN AMPLITUDE
AND TIMING. HOWEVER, BELOW NORMAL TEMPERATURES WITH SLIGHT
CHANCES OF PRECIPITATION MAY CONTINUE INTO THE BEGINNING OF NEXT
WEEK.
- FORECAST CONFIDENCE & SCENARIOS:
THERE REMAINS A DECENT SPREAD IN MOISTURE AMOUNTS WITH THIS
SYSTEM, WHICH WILL DEPEND ON HOW THESE TWO WAVES EVOLVE WITH EACH
OTHER. THERE ARE TWO FORCINGS WITH THIS SYSTEM CURRENTLY, THE
INCOMING CLOSED WAVE WITH THE FRONTAL PASSAGE AND THE TROUGH FROM
CANADA INTO THE ROCKY MOUNTAIN FRONT AND NORTH-CENTRAL MT. MODELS
HAVE A DECENT RANGE IN HOW MUCH PRECIPITATION IS ALONG AND BEHIND
THE FRONT. CURRENT PROBABILITIES GIVES A 40-70% CHANCE FOR 0.5"
OF MOISTURE FOR THE SOUTHWEST VALLEYS AND AN 80% CHANCE FOR THE
GALLATIN RANGE. PROBABILITIES DROP FARTHER NORTH INTO NORTH-
CENTRAL MT, WITH A 20-40% CHANCE FOR 0.5" OF MOISTURE. SNOW LEVELS
FALLING BEHIND THE FRONT GIVES MODERATE CONFIDENCE FOR SOME LIGHT
MOUNTAIN SNOW TO DEVELOP, WITH SOME MODEL RUNS GETTING LEVELS
DOWN TOWARDS 6,000FT FRIDAY IN SOUTHWEST MT. DEPENDING HOW MUCH
COLD AIR FROM THE SHORTWAVE TROUGH DIPPING DOWN FROM CANADA MOVES
INTO THE REGION, SNOW LEVELS MAY LOWER TO LOWER ELEVATIONS LATE
FRIDAY NIGHT INTO SATURDAY MORNING, BRINGING A RAIN/SNOW MIX. -WILSON
AVIATION
18/18Z TAF PERIOD
VFR CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD WITH PERIODS OF BROKEN
TO SCATTERED UPPER-LEVEL CLOUDINESS. OUTSIDE OF OCCASIONAL GUSTS
UP TO 15KTS, WINDS WILL GENERALLY REMAIN LIGHT AND VARIABLE FOR
MOST TERMINALS. -THOR
PRELIMINARY POINT TEMPS/POPS
GTF 38 71 40 56 / 0 0 0 0
CTB 31 61 36 54 / 0 0 0 0
HLN 33 68 35 62 / 0 0 0 0
BZN 33 67 36 63 / 0 0 0 10
WYS 22 59 26 57 / 0 0 0 20
DLN 33 64 35 62 / 0 0 0 10
HVR 35 65 35 60 / 0 0 0 0
LWT 36 71 41 56 / 0 0 0 0
TFX WATCHES/WARNINGS/ADVISORIES
NONE.
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