Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 220320
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
915 PM MDT THU MAY 21 2015

.UPDATE... LATEST RADAR IMAGERY SHOWS RAIN SHOWERS NEAR HELENA AND
PARTS OF BEAVERHEAD COUNTY CONTINUING TO SLOWLY DISSIPATE WHILE
SKIES ARE MOSTLY CLEAR ACROSS THE HILINE AND MOST OF THE CENTRAL MT
COUNTIES.  PRIMARY FORECAST ADJUSTMENT THIS EVENING WAS TO REDUCE
PRECIP CHANCES ACROSS JEFFERSON/BROADWATER/MADISON/GALLATIN COUNTIES
NOW THAT PRECIP HAS ENDED THERE.  PREDICTED OVERNIGHT TEMPERATURES
LOOK GOOD AT THIS TIME.
WARANAUSKAS

&&

.DISCUSSION...

TONIGHT THROUGH SATURDAY...RELATIVELY LIGHT UPPER LEVEL FLOW FROM
THE SOUTHEAST WILL CONTINUE OVERNIGHT BUT IS EXPECTED TO SHIFT
EAST-NORTHEAST AND INCREASE BY SATURDAY. SCATTERED TO NUMEROUS
SHOWERS AND A FEW THUNDERSTORMS CAN BE EXPECTED ACROSS SOUTHWEST
MONTANA THIS AFTERNOON AND EVENING BEFORE TAPERING OFF TO ISOLATED
SHOWERS OVERNIGHT. ISOLATED CONVECTION COULD REACH SOUTHERN PORTIONS
OF CENTRAL MONTANA THIS AFTERNOON AND EVENING AS WELL. HOWEVER,
FROM FRIDAY EVENING THROUGH SATURDAY AFTERNOON SCATTERED TO
NUMEROUS SHOWERS AND THUNDERSTORMS SPREAD ACROSS CENTRAL AND NORTH
CENTRAL MONTANA AS WELL. AS HAS BEEN MENTIONED OVER THE LAST FEW
DAYS, I AM NOT EXPECTED ANY SEVERE WEATHER AS CAPE AND SHEAR
REMAIN RELATIVELY WEAK. MPJ

FRIDAY NIGHT THROUGH TUESDAY...DO NOT SEE ANY WEATHER SYSTEMS THAT
WOULD HAVE A WIDESPREAD NEGATIVE IMPACT ON TRAVEL OR OUTDOOR
ACTIVITIES OVER THE LONG HOLIDAY WEEKEND. THERE WILL BE SEVERAL
UPPER LOWS TO CONTEND WITH DURING THE PERIOD BUT ALMOST ALL OF THEM
WILL NOT BE OVER THE FORECAST AREA. MODELS ARE IN BETTER AGREEMENT
TONIGHT WITH THEIR HANDLING THESE UPPER LOWS. ON SATURDAY ONE UPPER
LOW WILL BE OVER FAR SOUTHEAST MONTANA WITH ANOTHER OVER THE GREAT
BASIN AND A THIRD IN THE VICINITY OF THE PACIFIC NORTHWEST. NONE
WILL HAVE MUCH BEARING ON OUR FORECAST AREA. SCATTERED SHOWERS AND
POSSIBLY A FEW THUNDERSTORMS WILL BE DUE PRIMARILY TO UPSLOPE FLOW.
ON SUNDAY AN UPPER LOW WILL BE OVER THE WESTERN DAKOTAS WITH ANOTHER
IN THE AREA FROM NORTHERN CALIFORNIA TO TO OREGON. THERE MIGHT BE A
LITTLE LESS SHOWER ACTIVITY THEN ON SATURDAY. ON MEMORIAL DAY AN
UPPER LOW IS FORECAST TO BE OVER THE GREAT BASIN WHICH COULD LEAD TO
SCATTERED SHOWERS OR THUNDERSTORMS OVER SOUTHWEST MONTANA. FARTHER
NORTH MODELS DIFFER WITH THE GFS HAVING AN UPPER TROUGH OVER CENTRAL
MONTANA AND SCATTERED SHOWERS IN THAT SAME AREA. THE ECMWF ON THE
OTHER HAND DOES NOT SHOW THIS FEATURE AND IS DRY. TUESDAY
DIFFERENCES CONTINUE WITH THE UPPER AIR PATTERN AS THE ECMWF HAS AN
UPPER LOW OVER SOUTHERN IDAHO WITH SHOWERS OR THUNDERSTORMS FOR
SOUTHWEST MONTANA. THE GFS ON THE OTHER HAND HAS AN UPPER RIDGE OVER
IDAHO AND WESTERN MONTANA BUT DUE TO PRIMARILY TERRAIN EFFECTS
HAS SCATTERED SHOWERS OR THUNDERSTORMS MAINLY OVER THE WESTERN
MOUNTAINS. SEASONABLE HIGH TEMPERATURES MOSTLY IN THE 60S CAN BE
EXPECTED OVER THE HOLIDAY WEEKEND. BLANK

&&

.AVIATION... UPDATED 0000Z.

A RELATIVELY MORE MOIST/UNSTABLE AIRMASS HAS MOVED NORTH INTO SW MT
WITH SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS THIS
EVENING...MAINLY SOUTH OF KHLN TO KGTF. BRIEF MVFR CONDITIONS ARE
POSSIBLE UNDER THESE CELLS THIS EVENING WITH LOCAL TERRAIN
OBSCURATIONS. VFR CONDITIONS WILL PREVAIL OTHERWISE WITH SHOWERS AND
THUNDERSTORMS ENDING BY MIDNIGHT. EAST TO SOUTHEAST SURFACE WINDS
WILL CONTINUE THROUGH TOMORROW AND MAY BE LOCALLY GUSTY AT TIMES AT
THE KLWT AND KHVR TERMINALS. AREA OF MOISTURE/INSTABILITY SPREADS
FURTHER NORTH FRIDAY AFTERNOON WITH SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS POSSIBLE FURTHER NORTH INTO NORTH CENTRAL MT BY FRIDAY
EVENING. HOENISCH

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  43  70  46  67 /  10  20  30  40
CTB  37  69  41  68 /   0  10  10  20
HLN  45  72  48  67 /  30  30  30  60
BZN  39  69  42  64 /  30  40  30  50
WEY  32  61  34  58 /  40  50  60  60
DLN  41  66  44  64 /  50  40  30  50
HVR  38  73  43  73 /   0  10  30  20
LWT  41  69  45  64 /   0  40  40  40

&&

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

$$

WEATHER.GOV/GREATFALLS



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