Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 300555
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1155 PM MDT FRI APR 29 2016

AVIATION SECTION UPDATED

.UPDATE...
PLENTY OF CLOUD COVER ACROSS OUR REGION THIS EVENING, BUT ONLY
PRECIPITATION BEING OBSERVED IS SOME SCATTERED SHOWERS OVER FAR
SOUTHWEST MT ALONG AND A LITTLE NORTH OF THE MT/ID STATE LINE AND
OVER WESTERN TETON AND NORTHERN LEWIS & CLARK COUNTIES. LATEST
SATELLITE IMAGERY SHOWS ADDITIONAL MOISTURE BEGINNING TO STREAM
NORTHWARD INTO CENTRAL MT BETWEEN LEWISTOWN AND GREAT FALLS, BUT
THIS IS MOSTLY MID-LEVEL CLOUD COVER, SO EXPECTING LITTLE IF ANY
PRECIP OUT OF IT. WITH ADDITIONAL MOISTURE UPSTREAM NEAR BILLINGS
HEADING OUR WAY, CURRENT FORECAST FOR CONTINUED MOSTLY CLOUDY TO
OVERCAST SKIES TONIGHT IS ON TRACK. THE CLOUDS SHOULD ALSO LIMIT
RADIATIONAL COOLING OVERNIGHT SO HAVE NOT ADDED ANY MENTION OF FOG
FOR OVERNIGHT/EARLY MORNING HOURS. HOWEVER, MIDNIGHT SHIFT WILL
CONTINUE TO EVALUATE FOG SITUATION AND LATER INCLUSION OF FOG FOR SOME
LOCATIONS MAY BE NEEDED.
WARANAUSKAS

&&

.AVIATION...
UPDATED 0555Z.
UPDATED TAFS THIS EVENING INCLUDE REMOVING THE FOG. INCREASING
MID/HIGH CLOUDS SHOULD LIMIT THE POTENTIAL FOR FOG AT THE TERMINALS.
MAIN CONCERN WILL BE POTENTIAL FOR SHOWERS ON SATURDAY AFTERNOON.
HAVE ADDED A SMALL CHANCE FOR SHOWERS AT HELENA/BOZEMAN FOR SAT
AFTERNOON. ANY SHOWERS SHOULD BE BRIEF/LIGHT. OTHERWISE VFR
CONDITIONS SHOULD PREVAIL AT TERMINALS. MOUNTAINS WILL BE OBSCURED
AT TIMES THROUGH 00Z SUN THOUGH DUE TO MID CLOUDS. BRUSDA

&&

.PREV DISCUSSION...
/ISSUED 535 PM MDT FRI APR 29 2016/

TONIGHT THROUGH SUNDAY...MODELS APPEAR TO BE IN GOOD AGREEMENT FOR
THE WEEKEND WITH DRIER CONDITIONS AND A WARMING TREND EXPECTED BY
SUNDAY. A LARGE UPPER LEVEL TROUGH REMAINS OVER THE ENTIRE WESTERN
USA WITH A SECONDARY LOBE OVER WESTERN MONTANA. MODELS MOVE THIS
LOBE TO THE SOUTHWEST WHILE SIMULTANEOUSLY BUILDING THE UPPER
RIDGE CURRENTLY OVER THE EASTERN PACIFIC OCEAN INTO WESTERN
CANADA. A WEAK REX BLOCK PATTERN DEVELOPS THROUGH THE WEEKEND AS
HIGH PRESSURE ALOFT CONTINUES TO BUILD OVER WESTERN CANADA AND THE
UPPER LOW IS PUSHED SOUTHWARD INTO THE FOUR CORNERS REGION. THE
RESULT OF ALL THIS UPPER LEVEL ACTION WILL END UP GRADUALLY
REDUCING CLOUD COVER OVER MONTANA WITH MOSTLY CLEAR SKIES AND
SEASONABLY WARM TEMPERATURES RETURN ON SUNDAY. ISOLATED/SCATTERED
SHOWERS REMAIN POSSIBLE, MAINLY OVER THE MOUNTAINS, TONIGHT AND
SATURDAY. MPJ

SUNDAY NIGHT THROUGH FRIDAY...THE EXTENDED FORECAST PERIOD WILL
BEGIN WITH HIGH PRESSURE OVER ALBERTA AND AND LOW PRESSURE SOUTH OF
THE ZONES OVER NEVADA AND UTAH. THIS WILL KEEP THE AIRMASS OVER MOST
OF THE CWA QUITE DRY WITH MOISTURE OVER ONLY EXTREME SOUTHWEST
MONTANA. THIS HIGH PRESSURE CONTINUES TO KEEP THE AIRMASS DRY INTO
TUESDAY. HOWEVER, THE SOUTHWEST ZONES BECOME SLIGHTLY UNSTABLE
TUESDAY AFTERNOON, AND WITH THE MOISTURE JUST TO THE SOUTH, ISOLATED
SHOWERS OR THUNDERSTORMS ARE POSSIBLE. THE RIDGE WILL CONTINUE TO
STRENGTHEN THROUGH WEDNESDAY BUT A LOW PRESSURE TROF WILL BE MOVING
OVER THE WEST COAST LATE THURSDAY. HEIGHTS WILL BEGIN TO FALL ALOFT
AND AFTERNOON INSTABILITY WILL BRING SHOWERS OR THUNDERSTORMS ACROSS
CENTRAL AND SOUTHWEST MONTANA THURSDAY AND FRIDAY. THE AIRMASS WILL
CONTINUE TO MOISTEN FRIDAY NIGHT AS THE LOW PRESSURE TROF APPROACHES
AND SHOWERS WILL CONTINUE INTO THE NIGHT. THE AIRMASS WILL BE
TRENDING WARMER UNDER THE HIGH PRESSURE ALOFT. TEMPERATURES AT THE
BEGINNING OF THE PERIOD WILL BE NEAR OR ABOVE SEASONAL NORMALS AND
TREND HIGHER TO 15 TO 20 DEGREES ABOVE NORMALS BY THURSDAY. ZELZER

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  34  55  34  60 /  10  10   0   0
CTB  33  56  34  61 /  10  10  10   0
HLN  36  56  36  62 /  20  20  10   0
BZN  33  52  33  59 /  20  20  10  10
WEY  28  45  28  50 /  40  20  10  10
DLN  34  52  33  58 /  30  20  10  10
HVR  36  60  35  65 /  10  10   0   0
LWT  34  51  33  57 /  10  20  10   0

&&

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

&&

$$

WEATHER.GOV/GREATFALLS



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