Area Forecast Discussion
Issued by NWS Glasgow, MT

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000
FXUS65 KGGW 202040
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
240 PM MDT WED AUG 20 2014

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH FRIDAY...
UPPER TROUGH OVER THE WESTERN STATES WILL CONTINUE TO BE THE MAIN
WEATHER MAKER FOR MONTANA FOR THIS PERIOD. ONE DISTURBANCE
BRINGING THE SHOWERS TO THE EASTERN ZONES THIS AFTERNOON WILL BE
EXITING TO THE NE IN A FEW HOURS WITH THE NEXT ONE COMING INTO CWA
FROM THE WEST LATE TONIGHT AND MOVING THROUGH THURSDAY. MOST AREAS
LOOK TO PICK UP ABOUT A TENTH TO A QUARTER OF AN INCH OUT OF THIS
ONE.

A MORE SERIOUS RAINMAKER WILL BEGIN TO MOVE INTO CENTRAL MONTANA
FRIDAY AND THE TROUGH CLOSES OFF A BIT OVER THE PACIFIC NW.
THUNDERSTORMS DURING THIS PERIOD LOOK ISOLATED AT BEST AS 850-500 MB
LAPSE RATES SETTLE AROUND 6*C/KM.

THE OTHER STORY WILL BE THE COOL TEMPERATURES...ABOUT 10 TO POSSIBLY
20 DEGREES BELOW NORMAL. LOOKS LIKE WE WON/T BE SEEING 90 DEGREE
TEMPS FOR AWHILE.

WITH THE ANTICIPATED STEADY RAINFALL...FLOODING IS NOT EXPECTED TO
BE A CONCERN EVEN FOR THE RELATIVELY WET SE ZONES. FLASH FLOOD
GUIDANCE HAS COME UP SINCE THEIR RAINFALL A WEEK AGO. TFJ


.LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY...

GIVEN THE INCREASING TREND OF MODEL CONSENSUS IN THE EXTENDED
FORECAST PERIOD...FELT IT WAS WARRANT TO BEGIN PROVIDING A BIT
MORE DETAIL WITH PRECIPITATION TIMING...PLACEMENT...AND AMOUNTS.

AS THE MAIN AXIS OR LOW CENTER DIGS AND PIVOTS THROUGH THE WESTERN
STATES LOW PRESSURE TROUGH...CHANCES FOR PRECIP DRAMATICALLY
INCREASE. THIS IS PROGGED TO HAPPEN EARLY SATURDAY MORNING THROUGH
SUNDAY MORNING. GRANTED...THE CURRENT DEPICTION FOR SATURDAY AND
SUNDAY IS LOOKING VERY SIMILAR TO WHAT THE MODELS WERE SHOWING FOR
THURSDAY AND FRIDAY JUST A FEW DAYS AGO...BUT SINCE THEN HAVE
BACKED OFF ON QPF AMOUNTS BY ABOUT ONE HALF. SO YES...WE CAN
EXPECT WIDESPREAD RAIN ACCUMULATING FOR MOST LOCATIONS IN OUR
CWA...BUT AMOUNTS WILL PROBABLY NOT BE ANYTHING DRASTIC GIVEN THE
ABILITY OF OUR SE ZONES TO HANDLE THE RECENT 3 PLUS INCHES OF RAIN
FROM LAST WEEK WHICH HAS ALL BUT DRAINED THROUGH THE AREA BY NOW.

AFTER A COOL WEEKEND...CAN EXPECT A SLIGHT WARM UP LEADING INTO
THE BEGINNING OF NEXT WEEK TO ACTUALLY QUITE COMFORTABLE LEVELS
FOR THIS TIME OF YEAR.

MADE MOST OF THE ADJUSTMENTS FOLLOWING PERSISTENT MODEL CONSENSUS
DEPICTED IN THE EXTENDED MODEL DATA. BMICKELSON

PREVIOUS LONG TERM DISCUSSION...THE EXTENDED PERIOD BEGINS ON FRIDAY
NIGHT WITH THE LARGE TROUGH ACROSS THE WESTERN U.S. PUSHING
SOUTHWEST FLOW ALOFT OVER NORTHEAST MONTANA. ABUNDANT MOISTURE AND
PLENTY OF UPPER LEVEL DYNAMIC SUPPORT WILL LEND TO PERIODS OF RAIN
CONTINUING THROUGH SATURDAY WITH PERHAPS SOME EMBEDDED THUNDER.
WRAP-AROUND SHOWER ACTIVITY WILL CONTINUE...ESPECIALLY EAST...INTO
SUNDAY AS WELL AS SURFACE LOW TRACKS INTO SOUTHERN MANITOBA. IN
FACT...GUIDANCE IS HAS TRENDED TOWARD A SOLUTION WITH A SLOWER
PROGRESSION OF THIS EVENT. AS THE STORM SYSTEM BECOMES VERTICALLY
STACKED OVER SOUTHERN MANITOBA ON MONDAY...ISOLATED SHOWERS MAY
STILL BE POSSIBLE ACROSS NORTHEAST MONTANA. BY THE TIME ALL IS
SAID AND DONE...WIDESPREAD WETTING RAINS ARE LIKELY. SPECIFIC
TIMING AND DETAILS ARE STILL SOMEWHAT UNCERTAIN. THE TROUGH IN
PLACE WILL ALSO MEAN RELATIVELY LOW 500-1000 MB THICKNESSES ACROSS
MONTANA. THEREFORE...TEMPERATURES WILL BE WELL BELOW AVERAGE
THROUGH EARLY NEXT WEEK.

TUESDAY ONWARD...ENSEMBLE OF 500MB HEIGHTS BEGIN TO SHOW
INCREASINGLY LARGER SPREAD...LENDING TO LOWERING CONFIDENCE. THE
20/00Z ECMWF AND GFS EACH SHOW THE POTENTIAL FOR RIDGING ACROSS
THE REGION TOWARD THE MIDDLE OR END OF NEXT WEEK.
HOWEVER...DIFFERENCES IN TIMING/EVOLUTION/CHARACTERISTICS OF
SYNOPTIC FEATURES ARE LARGE ENOUGH THIS FAR OUT THAT IT IS
DIFFICULT TO ADD MUCH INSIGHT AS TO WHAT PRECIPITATION CHANCES MAY
RESULT. FOR NOW WILL TREND POPS TO NEAR CLIMO FOR THE END OF THE
LONG RANGE. AS AT LEAST THE POTENTIAL EXISTS FOR RIDGING ONCE THE
LARGE TROUGH LOSES INFLUENCE ON THE CWA...WILL GRADUALLY TREND
TEMPERATURES UPWARD AS WELL FOR THE MIDDLE OF NEXT WEEK. MALIAWCO

&&

.AVIATION...

IN GENERAL...EXPECT VFR CONDITIONS TO PREVAIL...ALTHOUGH MAINLY
SCATTERED RAIN SHOWERS AND PERHAPS A THUNDERSTORM MAY CAUSE BRIEF
RESTRICTED VISIBILITIES ACROSS THE TAF SITES LATER TODAY AS SOME
AREAS SEE CEILINGS DROP TO AROUND 5000 FEET. EXPECT NEAR NORTHERLY
WINDS AROUND 10-15 KTS BECOMING LIGHT AND VARIABLE TONIGHT.
MALIAWCO/BMICKELSON


&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

WEATHER.GOV/GLASGOW





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