634
FXUS65 KTFX 091133
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
533 AM MDT SAT MAY 9 2026
AVIATION SECTION UPDATED.
KEY MESSAGES
- SLIGHTLY COOLER TEMPERATURES AND SCATTERED SHOWER AND
THUNDERSTORM ACTIVITY WILL CONTINUE TODAY, MOST NUMEROUS OVER
CENTRAL AND NORTH- CENTRAL MONTANA.
- VERY WARM, MOSTLY DRY, AND BREEZY TO LOCALLY WINDY
CONDITIONS DEVELOP LATE SUNDAY THROUGH MID- WEEK.
- SHOWER AND THUNDERSTORM ACTIVITY INCREASES FOR THE SECOND HALF
OF THE WORK WEEK, ALONG WITH MORE BREEZY TO WINDY CONDITIONS.
- NEXT WEEKEND LOOKS TO FEATURE SLIGHTLY COOLER TEMPERATURE WITH
CONTINUED SCATTERED SHOWER AND ISOLATED THUNDER ACTIVITY.
DISCUSSION
/ISSUED 243 AM MDT SAT MAY 9 2026/
- METEOROLOGICAL OVERVIEW:
THE SHORTWAVE TROUGH RESPONSIBLE FOR THE SHOWER ACTIVITY THIS
MORNING WILL MOVE SOUTHEAST OF THE FORECAST AREA BY AROUND NOON,
THOUGH LINGERING INSTABILITY BEHIND THIS SYSTEM WILL MAINTAIN
WIDELY SCATTERED SHOWER AND THUNDER ACTIVITY OVER CENTRAL AND
NORTH-CENTRAL MT.
TRANSIENT RIDGING ALOFT QUICKLY REPLACES THE DEPARTING WAVE AND
BRINGS MUCH WARMER AND DRIER CONDITIONS BY SUNDAY AFTERNOON.
SURFACE WINDS WILL BEGIN INCREASING LATE SUNDAY THROUGH MONDAY IN
RESPONSE TO A ANOTHER SHORTWAVE MOVING EASTWARD ALONG THE CANADIAN
BORDER. THE PRIMARY CONCERN WITH THE WINDS WILL BE AT LEAST A
BRIEF PERIOD ELEVATED FIRE WEATHER CONDITIONS, PARTICULARLY ALONG
THE HI-LINE AND DOWN IN THE SOUTHWEST WHERE ANTECEDENT GROUND
CONDITIONS ARE DRIEST. THE PASSING SHORTWAVE WILL HAVE LITTLE
IMPACT ON TEMPERATURES WITH AFTERNOON HIGHS CONTINUING TO RUN
MOSTLY IN THE 70S AND 80S FOR LOWER ELEVATION LOCATIONS.
A CLOSED MID-LEVEL TROUGH MOVING ONTO THE PACIFIC COAST WILL
BRING A MORE UNSTABLE SOUTHEASTERLY FLOW ALOFT FOR THE WEDNESDAY
THROUGH FRIDAY PERIOD. THIS WILL INTRODUCE DAILY ROUNDS OF SHOWER
AND THUNDERSTORM ACTIVITY, SOME OF WHICH MAYBE ON THE STRONGER
SIDE WITH CAPE VALUES APPROACHING 1,000 J/KG ON SOME DAYS. WINDY
CONDITIONS LOOK TO DEVELOP WHEN THE TROUGH AND ATTENDANT COLD
FRONT APPROACHES EITHER THURSDAY OR FRIDAY. ENSEMBLE GUIDANCE
CONTINUES TO DISPLAY DISAGREEMENTS WITH THE TIMING OF THE TROUGH
AND THIS WILL HAVE A SIGNIFICANT IMPACT ON THE TIMING OF
THUNDERSTORM ACTIVITY AND THE STRONGEST WINDS. THE OVERALL
UNSETTLED WEATHER PATTERN LOOKS TO CONTINUE HEADING INTO NEXT
WEEKEND WITH MORE PACIFIC TROUGHS APPROACHING THE NORTHERN
ROCKIES. - RCG
- FORECAST CONFIDENCE & SCENARIOS:
WINDS AND FIRE WEATHER CONCERNS LATE SUNDAY AND MONDAY...
A SHORTWAVE TROUGH RACES EASTWARD ALONG THE CANADIAN BORDER
SUNDAY NIGHT INTO MONDAY AND BRINGS BREEZY TO WINDY CONDITIONS
OVER MUCH OF THE FORECAST AREA. WINDS WILL INCREASE ALONG THE
ROCKY MOUNTAIN FRONT AND ADJACENT HIGH PLAINS LATE SUNDAY
AFTERNOON WITH GUSTS OVER 50 MPH AT TIMES SUNDAY NIGHT THROUGH
MONDAY MORNING. THE REMAINDER OF THE FORECAST ARE WILL GENERALLY
SEE WIND GUSTS MOSTLY IN THE 25 TO 40 MPH RANGE DURING THE DAY ON
MONDAY. THE EXCEPTION TO THIS WILL BE OVER HILL AND BLAINE
COUNTIES AND AGAIN ALONG THE ROCKY MOUNTAIN FRONT AND NEARBY HIGH
PLAINS. THESE AREAS CURRENTLY HAVE A 60 TO 90% CHANCE FOR GUSTS
OVER 40 MPH. THE COMBINATION OF WINDS, NEAR OR CRITICALLY LOW
MINIMUM RHS, AND DRY ANTECEDENT CONDITIONS WILL BRING THE HIGHEST
FIRE RISK TO HILL AND BLAINE COUNTIES ON MONDAY. THE ONE
UNCERTAINTY THAT MAY PRECLUDE AN EXTENDED PERIOD OF ELEVATED TO
CRITICAL FIRE WEATHER CONDITIONS WILL BE INCREASING HUMIDITIES
BEHIND A SURFACE FRONT MONDAY AFTERNOON. HELD OFF ISSUING A FIRE
WEATHER WATCH FOR NOW GIVEN LOW CONFIDENCE OF AN EXTENDED PERIOD
OF CRITICAL CONDITIONS, BUT THE SITUATION WILL CONTINUE TO BE
MONITORED.
INCREASED SHOWER AND THUNDERSTORM ACTIVITY AND WINDS WEDNESDAY
THROUGH FRIDAY...
ENSEMBLES CONTINUE TO AGREE ON A MORE UNSTABLE SOUTHWESTERLY FLOW
DEVELOPING AND BRINGING MULTIPLE ROUNDS OF SHOWER AND
THUNDERSTORM ACTIVITY DURING THIS TIMEFRAME; HOWEVER, THERE ARE
INCONSISTENCIES ON WHICH DAY WILL HAVE THE HIGHEST CAPE IN THE 500
TO 1,000 J/KG RANGE. OVERALL, THERE IS AN EXPECTATION FOR DAILY
LIGHTNING AND GUSTY WIND THREATS GIVEN AT LEAST A FEW HUNDRED
JOULES OF CAPE AND VERY WARM AND DRY SUB CLOUD LAYERS. THE TIMING
OF THE TROUGH AND ASSOCIATED SHORTWAVES WILL ULTIMATELY DETERMINE
WHICH DAY WILL SEE THE MOST ROBUST CONVECTIVE ACTIVITY AND SEVERE
HAIL/WIND THREAT.
AROUND A QUARTER OF THE ENSEMBLES WERE HIGHLIGHTING THE TROUGH
EJECTING EASTWARD INTO THE NORTHERN ROCKIES AS EARLY AS LATE
WEDNESDAY INTO THURSDAY AND BRINGING WIDESPREAD STRONG WINDS WITH
IT. THE NEWER DETERMINISTIC GUIDANCE SEEMS TO BE BACKING OFF OF
THIS SOLUTION, THOUGH ANOMALY INDICES, INCLUDING THE ECMWF EXTREME
FORECAST INDEX STILL HAVE A WEAK SIGNAL FOR ANOMALOUSLY STRONG
WINDS AND NBM PROBABILISTIC GUIDANCE STILL PAINTS A DAILY 20 TO
30% CHANCE FOR GUSTS OVER 55 MPH FOR MUCH OF THE FORECAST AREA
WEDNESDAY THROUGH FRIDAY. BOTH THE THUNDERSTORM ACTIVITY AND WIND
SITUATIONS WILL BE MONITORED FOR THIS TIMEFRAME IN THE COMING
DAYS. - RCG
AVIATION
09/12Z TAF PERIOD
AN AREA OF CONCENTRATED SHOWERS AND ASSOCIATED LOW VFR/MVFR
CONDITIONS AND MOUNTAIN OBSCURATION OVER AND NEAR THE CENTRAL
ISLAND RANGES WILL CONTINUE TO MOVE SOUTHEAST AND DIMINISH AS THE
MORNING PROGRESSES. THERE WILL BE LINGERING INSTABILITY FOR
ADDITIONAL WIDELY SCATTERED SHOWERS AND ISOLATED THUNDER OVER
CENTRAL AND NORTH-CENTRAL MT BETWEEN 09/18 AND 10/00Z. PARTIAL
CLEARING TAKES PLACE TONIGHT WITH SOME PATCHY FOG DEVELOPMENT LATE
TONIGHT INTO SUNDAY MORNING, MOSTLY OVER THE RIVER VALLEYS.
CONFIDENCE WAS TOO LOW TO MENTION FOG IN ANY TAF FOR TONIGHT.
- RCG
FIRE WEATHER
VERY WARM, DRY, AND BREEZY TO LOCALLY WINDY CONDITIONS DEVELOP LATE
SUNDAY INTO EARLY NEXT WEEK WITH THE DRIEST AND WINDIEST DAY LOOKING
TO BE MONDAY. HILL AND BLAINE COUNTIES CURRENTLY HAVE THE DRIEST
ANTECEDENT GROUND CONDITIONS AND WILL HAVE OVER 70% CHANCE FOR WIND
GUSTS OVER 40 MPH. DRY FUELS ARE ALSO BEING OBSERVED OVER SOUTHWEST
MONTANA AS WELL, BUT THE STRONGER WINDS WILL BE MORE LOCALIZED IN
THESE AREAS. THE ONE FACTOR THAT MAY PRECLUDE AN EXTENDED PERIOD OF
ELEVATED TO CRITICAL FIRE WEATHER CONDITIONS ALONG THE HI-LINE WILL
BE INCREASING HUMIDITIES BEHIND A CANADIAN SURFACE FRONT MONDAY
AFTERNOON. BE MINDFUL OF THE UPCOMING VERY WARM AND DRY CONDITIONS
AND AVOID ACTIVITIES INVOLVING SPARKS OR OPEN FLAMES. - RCG
PRELIMINARY POINT TEMPS/POPS
GTF 66 43 82 55 / 80 10 0 0
CTB 65 41 78 51 / 30 10 0 0
HLN 69 41 81 50 / 10 0 0 0
BZN 66 36 79 46 / 10 0 0 0
WYS 61 30 72 39 / 0 0 0 0
DLN 66 37 80 47 / 0 0 0 0
HVR 69 40 82 52 / 20 10 0 0
LWT 59 39 77 50 / 90 20 0 0
TFX WATCHES/WARNINGS/ADVISORIES
NONE.
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