Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 290540
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1145 PM MDT THU APR 28 2016

AVIATION SECTION UPDATED

.UPDATE...
AREAS OF LIGHT RAIN AND RAIN/SNOW MIX HAVE BEEN GRADUALLY
DISSIPATING ACROSS THE REGION THIS EVENING AS THE UPPER-LEVEL LOW
PRESSURE CENTER BRINGING IN THE MOISTURE HAS MOVED WEST TO THE
IDAHO-MONTANA BORDER SOUTHWEST OF MISSOULA. LATEST SATELLITE
IMAGERY STILL SHOWS WIDESPREAD LOW- AND MID-LEVEL CLOUD COVER
OVER CENTRAL/SOUTHWEST MT, MUCH OF WHICH WILL REMAIN IN PLACE
OVERNIGHT.

MAIN CONCERN THIS EVENING AND INTO FRI MORNING IS FOG DEVELOPMENT
AROUND THE REGION. WITH THE GROUND WELL-SATURATED IN MANY SPOTS
FROM PRECIP THE PAST FEW DAYS AND CURRENT DEW POINTS IN THE UPPER
20S TO MID 30S, IT WON`T TAKE MUCH OF A TEMPERATURE DROP FROM
BREAKS IN THE CLOUDS OR OVERNIGHT COOLING TO SET UP AREAS OF FOG.
CURRENT FORECAST ALREADY INCLUDES MENTION OF PATCHY FOG AT ALL
VALLEY/PLAINS LOCATIONS AND HAVE LEFT THAT UNCHANGED WITH THE
EVENING UPDATE. NOT ENOUGH CONFIDENCE AT THIS POINT TO GO FOR MORE
WIDESPREAD DENSE FOG AS THE CURRENT OVERCAST CONDITIONS MAY LIMIT
COOLING IN VARIOUS LOCATIONS. EITHER WAY, DRIVERS SHOULD BE
PREPARED TO ENCOUNTER LIMITED VISIBILITY ALONG TRAVEL ROUTES
TOMORROW MORNING.

ONLY FORECAST ADJUSTMENT THIS EVENING WAS TO REDUCE PRECIP
PROBABILITIES FROM GREAT FALLS SOUTH- AND EASTWARD TO
HELENA/BOZEMAN/LEWISTOWN TO BETTER MATCH CURRENT RADAR IMAGERY AND
OBSERVATIONS. WARANAUSKAS

&&

.AVIATION...
UPDATED 0545Z.
GENERALLY WIDESPREAD LOW/MID CLOUDS CONTINUE TO AFFECT MUCH OF
REGION...WITH MOUNTAINS OBSCURED. THAT TREND WILL CONTINUE THROUGH
FRIDAY MORNING. SOME PATCHY FOG IS POSSIBLE AROUND 12Z IN MANY
AREAS...BUT SINCE THE CLOUDS ARE SLOW TO BREAK UP...CONFIDENCE IS
LOW IN HOW THICK THE FOG WILL GET. A FEW SHOWERS ARE POSSIBLE ON
FRIDAY AFTERNOON...BUT MAINLY OVER THE WESTERN/SOUTHWESTERN
MOUNTAINS. BRUSDA

&&

.PREV DISCUSSION...
/ISSUED 540 PM MDT THU APR 28 2016/

TONIGHT THROUGH SATURDAY...THE WIDESPREAD PRECIPITATION WILL
GRADUALLY TRANSITION TO A MORE SHOWERY WEATHER PATTERN INTO THIS
WEEKEND. A WEAK LOW PRESSURE AREA WITHIN THE MAIN TROUGH OVER THE
AREA WILL MOVE NORTH ACROSS WESTERN MONTANA OVERNIGHT,
ESSENTIALLY CUTTING OFF THE MOISTURE FEED FROM THE EAST. AS A
RESULT, THE RAIN AND MOUNTAIN SNOW OVER THE FORECAST AREA WILL
BECOME MORE SHOWERY AND DIMINISH OVERNIGHT. HOWEVER, BREAKS IN THE
CLOUDS WITH LIGHTER WINDS WILL COMBINE WITH THE LOW LEVEL
MOISTURE TO POSSIBLY CAUSE PATCHY FOG TO DEVELOP IN SOME AREAS,
MOSTLY AFTER MIDNIGHT AND INTO FRIDAY MORNING. AN UPPER LEVEL LOW
PRESSURE TROUGH WILL THEN DEEPEN ALONG THE PACIFIC NORTHWEST COAST
ON FRIDAY AND MOVE INTO WESTERN MONTANA ON SATURDAY. THIS WILL
PLACE A WARMER AND MORE UNSTABLE SOUTHERLY FLOW ALOFT OVER THE
AREA. THIS WILL RESULT IN MAINLY AFTERNOON AND EVENING SCATTERED
SHOWERS, WITH POSSIBLY A FEW WEAK THUNDERSTORMS, THAT WILL SPREAD
WEST TO EAST ACROSS THE FORECAST AREA FRIDAY INTO SATURDAY. ALSO,
TEMPERATURES WILL WARM THROUGH THIS PERIOD FROM SLIGHTLY BELOW
NORMAL TODAY TO SLIGHTLY ABOVE NORMAL BY SATURDAY.  COULSTON

SATURDAY NIGHT THROUGH THURSDAY...MEDIUM RANGE MODELS COMING INTO
BETTER AGREEMENT WITH BRINGING AN END TO THE COOL UNSETTLED
PATTERN OF THE PAST WEEK. THE ELONGATED UPPER TROF WEAKENS TO
START THE PERIOD AS THE ASSOCIATED DEFORMATION ZONE DRIFTS
FURTHER SOUTH IN RESPONSE TO HIGH PRESSURE THAT BEGINS BUILDING
ACROSS THE NORTH. ISOLATED SHOWERS SATURDAY NIGHT WILL BE
CONFINED TO PORTIONS OF SOUTHWEST MONTANA AND TO THE WESTERN
MOUNTAINS. THE UPPER TROF SPLITS ON SUNDAY WITH THE WESTERN
PORTION RESIDING OVER NEVADA/UTAH AND THE EASTERN PORTION FILLING
AS IT PUSHES INTO THE UPPER MIDWEST. CIRCULATION AROUND THE
WESTERN LOBE WILL CONTINUE TO BRING SOME SHOWERS TO THE WESTERN
AND SOUTHWEST MOUNTAINS. HIGH PRESSURE WILL THEN BUILD OVER THE
AREA MONDAY USHERING IN WARMER AND DRY CONDITIONS THAT WILL
CONTINUE THROUGH THE REMAINDER OF THE PERIOD. TEMPERATURES WILL
BE NEAR SEASONAL AVERAGES SUNDAY BUT WILL CONTINUE TO SLOWLY WARM
EACH DAY THROUGH THURSDAY.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  30  53  34  57 /  30  20  20  20
CTB  30  52  33  57 /  20  20  20  30
HLN  32  57  36  59 /  20  30  30  30
BZN  31  55  34  56 /  20  20  20  30
WEY  27  48  29  49 /  20  40  40  30
DLN  29  54  34  55 /  20  40  30  30
HVR  33  56  36  60 /  10  10  10  20
LWT  31  50  34  54 /  30  10  20  20

&&

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

&&

$$

WEATHER.GOV/GREATFALLS



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