Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 180454
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1055 PM MDT FRI APR 17 2015

UPDATED AVIATION SECTION

.DISCUSSION...

UPDATE FORTHCOMING. HAVE MADE ADJUSTMENTS TO THE SKY GRID TO BETTER
REFLECT SOME HIGH CLOUDS MOVING ACROSS THE HI-LINE AS DEPICTED BY
SATELLITE IMAGERY. REMAINDER OF FORECAST LOOKS ON TRACK. UPPER RIDGE
WILL FLATTEN AS AN UPPER TROF MOVES ACROSS SOUTHERN CANADA TONIGHT.
AN ASSOCIATED COLD FRONT WILL MOVE RAPIDLY SOUTH
OVERNIGHT...REACHING CENTRAL MONTANA BY DAYBREAK AND SOUTHWEST
MONTANA BY MID MORNING. GUSTY NORTH WINDS WILL ACCOMPANY THE FRONT.
00Z NAM MODEL IS COMING IN WITH EVEN LESS QPF THAN PREVIOUSLY
THOUGHT. MID SHIFT WILL MAKE A FINAL DETERMINATION AFTER ALL 00Z
RUNS ARE IN.

&&

.AVIATION...
UPDATED 0455Z.

A DISTURBANCE ALOFT WILL MOVE SOUTHEAST FROM SOUTHERN BRITISH
COLUMBIA AND SOUTHERN ALBERTA ACROSS MONTANA THROUGH THE DAY ON
SATURDAY. AN ASSOCIATED COLD FRONT WILL MOVE SOUTH OF CANADIAN
BORDER AFTER 06Z, CAUSING WINDS TO SHIFT MORE NORTHERLY AND BECOME
QUITE GUSTY (20 TO 30 KT GUSTS AT TIMES) AT KCTB AND KHVR BETWEEN
08Z AND 11Z, AT KGTF, KLWT, AND KHLN BETWEEN 11Z AND 14Z, AND AT
KBZN BETWEEN 15Z AND 17Z. THE BEST CHANCE FOR SCATTERED RAIN AND
MOUNTAIN SNOW SHOWERS WILL ACCOMPANY FRONTAL PASSAGE AND CONTINUE
FOR A FEW HOURS AFTERWARD, POTENTIALLY CAUSING OCCASIONAL MVFR
CONDITIONS AND MOUNTAIN OBSCURATION. CONDITIONS WILL OTHERWISE BE
VFR. PRECIPITATION WILL DECREASE FROM THE NORTHWEST AFTER 16Z AS THE
DISTURBANCE BEGINS EXITING THE AREA, BUT MID LEVEL CLOUDINESS AND
GUSTY NORTHERLY WINDS WILL PERSIST THROUGH THE REMAINDER OF THE DAY.
COULSTON

&&

.PREV DISCUSSION...ISSUED 308 PM MDT FRI APR 17 2015

TONIGHT THROUGH SUNDAY...A WEAK UPPER LEVEL RIDGE WILL MOVE EAST OF
THE ZONES TONIGHT AS A LOW PRESSURE SHORTWAVE APPROACHES THE ROCKIES
FROM THE WEST. AN ASSOCIATED COLD FRONT WILL CROSS THE CANADIAN
BORDER BY SUN RISE AND MOVE SOUTH THROUGH THE ZONES DURING THE
MORNING. WINDS ALOFT WILL STRENGTHEN AS THE SHORTWAVE APPROACHES AND
SWITCH TO THE NORTH WITH FRONTAL PASSAGE. WINDS WILL BECOME STRONG
AND GUSTY BEHIND THE FRONT. THE MODELS ONLY GENERATE WEAK LIFT WITH
THIS SYSTEM AND THE AMOUNT OF AVAILABLE MOISTURE WILL REMAIN LOW, SO
MOST PRECIP IS EXPECTED ALONG WITH FRONTAL PASSAGE. AND SINCE SINCE
THE LOW LEVELS WILL REMAIN FAIRLY DRY, UPSLOPE SHOULD NOT PRODUCE
MUCH ADDITIONAL PRECIPITATION. THE SOUTHWEST ZONES MIGHT BECOME A
BIT UNSTABLE SATURDAY AFTERNOON BUT UPPER LEVELS WILL REMAIN WARM
AND SHOULD CAP ANY SIGNIFICANT DEVELOPMENT. SNOW LEVELS WILL BE
QUITE HIGH SATURDAY MORNING AND, ALONG WITH THE LACK OF MOISTURE,
SNOWFALL SHOULD NOT BE AN IMPACT. THE SHORTWAVE WILL MOVE EAST OF
THE ZONES SATURDAY NIGHT AND PRESSURE ALOFT WILL BUILD. A FEW WEAK
DISTURBANCES MOVE THROUGH THE FLOW ALOFT SUNDAY AND KEEP SOME
THREAT OF SHOWERS BUT THE CHANCE WILL REMAIN LOW.

SUNDAY NIGHT THROUGH FRIDAY...THE WEATHER PATTERN STARTS OUT FAIRLY
QUIET TO BEGIN THE EXTENDED PERIOD...AS AN UPPER LEVEL RIDGE OF HIGH
PRESSURE BUILDS OVER THE REGION THROUGH TUESDAY. EXPECT A GRADUAL
WARMING TREND FOR MONDAY AND TUESDAY...WITH AFTERNOON HIGHS NEAR 70
DEGREES BY TUESDAY. ON WEDNESDAY...AN UPPER LEVEL DISTURBANCE WILL
BE SLIDING SOUTHWARD THROUGH THE SOUTHERN PORTION OF THE U.S. THIS
WILL RESULT IN SHOWERS TRYING TO PUSH NORTHWARD INTO SOUTHWEST MT.
THE PRECIP COULD MAKE IT AS FAR NORTH AS CENTRAL MT BY WEDNESDAY
NIGHT. THE CHANCE FOR SHOWERS WILL CONTINUE FOR THURSDAY AND
FRIDAY...BUT ANY PRECIPITATION IS EXPECTED TO BE LIGHT AND FAIRLY
HIT/MISS RIGHT NOW. BRUSDA

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  39  52  30  52 /  10  50  10  10
CTB  37  50  28  51 /  30  50  10  10
HLN  35  53  30  53 /   0  40  10  10
BZN  33  55  30  51 /   0  30  10  10
WEY  28  49  25  45 /   0  30  10  20
DLN  32  57  30  53 /  10  30  10  20
HVR  40  55  29  53 /  10  30  10  10
LWT  38  48  28  47 /   0  30  10  10

&&

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

$$

WEATHER.GOV/GREATFALLS


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