Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 191125
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
525 AM MDT SUN APR 19 2015

AVIATION SECTION UPDATED

.DISCUSSION...
TODAY THROUGH TUESDAY EVENING...SHORT-TERM FORECAST PERIOD SHAPING
UP TO BE RELATIVELY UNEVENTFUL WITH MOSTLY DRY CONDITIONS AND
GRADUALLY WARMING TEMPERATURES FOR THE FIRST HALF OF THE WEEK.  WITH
A DEEP LOW PRESSURE TROF OVER THE MIDWEST STATES AND HIGH PRESSURE
RIDGING ALONG THE WEST COAST, CENTRAL AND SOUTHWEST MONTANA WILL
REMAIN UNDER NORTHWEST FLOW ALOFT THROUGH MONDAY WITH OCCASIONAL
BANDS OF MOISTURE SLIDING THROUGH THE FLOW.  THIS WILL RESULT IN
PERIODS OF WIDESPREAD MID- AND HIGH-LEVEL CLOUDS COVERING AREAS
ALONG AND WEST OF THE INTERSTATE 15 CORRIDOR, WITH LESS CLOUD
COVER FURTHER EAST. OTHER THAN A SLIGHT CHANCE FOR A STRAY SHOWER
OR TWO ALONG THE ROCKY MTN FRONT AND HIGH PEAKS OF THE SOUTHWEST
MTNS, NO PRECIPITATION IS EXPECTED OVER THE NEXT 48 HRS. THE
PACIFIC RIDGE WILL MAKE VERY SLOW EASTWARD PROGRESS THROUGH THE
PERIOD, BECOMING CENTERED ALONG THE WA/OR/ID BORDER BY MIDDAY
TUES. THIS WILL ALLOW THE WINDS ALOFT TO GRADUALLY TURN TO THE
WEST-SOUTHWEST, WHICH WILL BRING SOME MOISTURE FROM IDAHO INTO THE
SOUTHWEST COUNTIES. THE MOISTURE WILL COMBINE WITH SLIGHTLY
UNSTABLE CONDITIONS (CAPE VALUES OF 150-200 J/KG AND LIFTED
INDICES OF -1 TO -2) TO GIVE A CHANCE FOR ISOLATED THUNDERSTORMS
ALONG/SOUTH OF LINE FROM WISDOM-TO-ENNIS-TO-BIG SKY ON TUES
AFTN/EVE. AS FOR TEMPERATURES, MOST OF THE REGION WILL SEE MID 50S
TODAY, THEN WARMING TO THE UPPER 50S TO LOW 60S ON MON, AND
INCREASING TO UPPER 60S ON TUES.
WARANAUSKAS


TUESDAY NIGHT THRU SUNDAY...EXPECT THE WEATHER PATTERN TO SLOWLY
BECOME A BIT MORE ACTIVE AS WE MOVE INTO THE SECOND HALF OF THE WORK
WEEK. THE UPPER LEVEL RIDGE OF HIGH PRESSURE THAT WILL BE OVER THE
REGION FOR THE FIRST HALF OF THE WEEK...WILL SLOWLY BEGIN TO BREAK
DOWN DURING THE SECOND HALF OF THE WEEK. WITH THE AIRMASS BECOMING A
BIT UNSTABLE DURING THE AFTERNOON AND EVENING HOURS...THERE WILL BE
A CHANCE FOR MAINLY AFTERNOON SHOWERS AND THUNDERSTORMS OVER CENTRAL
AND SOUTHWEST MT FROM WED THRU FRI. MOST OF THE THUNDERSTORM
ACTIVITY SHOULD BE CONFINED TO THE SOUTHERN PORTIONS OF THE
REGION...WHERE THE AIRMASS WILL BE A BIT MORE UNSTABLE. TEMPERATURES
WILL BE MILD ON WEDNESDAY...THEN GRADUALLY COOL A BIT FOR THURSDAY
AND FRIDAY. FOR NEXT WEEKEND...BOTH MODELS HAVE A WEATHER SYSTEM
MOVING THRU THE REGION...BUT THEY DIFFER ON THE EXACT TIMING AND
STRENGTH. THE GFS MODEL IS SLOWER AND PRODUCES ALONG PERIOD OF RAIN
AND HIGHER QPF AMOUNTS...WHILE THE EC IS FASTER AND NOT AS WET. THUS
FOR NOW I INCREASED POPS A BIT FOR SATURDAY NIGHT INTO
SUNDAY...ESPECIALLY OVER SOUTHWEST MT. MOST OF THE PRECIPITATION
WILL BE RAIN...BUT THERE WILL BE A CHANCE FOR SNOW FOR ELEVATIONS
MAINLY ABOVE 5000 FEET BY SUNDAY MORNING. TEMPERATURES WILL ALSO
COOL TO NEAR NORMAL READINGS BY SUNDAY.
BRUSDA

&&

.AVIATION...
UPDATED 1125Z. VFR CONDITIONS EXPECTED.  POCKETS OF MOISTURE
STREAMING THROUGH NORTHWEST FLOW ALOFT WILL BRING MIX OF HIGH
SCATTERED CLOUDS AND SOME MID-LEVEL (5000-8000 FT) CEILINGS ACROSS
CENTRAL AND SOUTHWEST MT THROUGH THIS EVENING. CAN`T RULE OUT A FEW
STRAY SHOWERS OVER THE SOUTHWEST MOUNTAIN RANGES, INCLUDING BRIDGERS
NEAR KBZN, BUT PROBABILITY IS LOW FOR PRECIP AT TAFS SITES TODAY.
STILL KEEPING AN EYE ON POSSIBLE FOG DEVELOPMENT AT KGTF THIS
MORNING AS TEMPERATURE-DEW POINT SPREAD IS JUST 2 DEGREES AT 11Z,
BUT NOT ENOUGH CONFIDENCE TO INCLUDE IT IN 12Z TAF AT THIS POINT.
WARANAUSKAS

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  54  33  63  38 /  10   0   0  10
CTB  54  32  63  37 /  10   0   0  10
HLN  57  31  65  35 /  10  10   0  10
BZN  53  29  60  34 /  20  10   0  10
WEY  50  27  55  28 /  20  10  10   0
DLN  56  32  62  33 /  20  10  10   0
HVR  55  31  61  37 /   0   0   0   0
LWT  50  29  57  35 /  10   0   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

WEATHER.GOV/GREATFALLS



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