Area Forecast Discussion
Issued by NWS Glasgow, MT

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS65 KGGW 220208
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
808 PM MDT THU AUG 21 2014

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH SATURDAY...
UPDATE...NUMEROUS SHOWERS CONTINUE ACROSS THE REGION THIS EVENING
AND LOOK TO CONTINUE OVERNIGHT. ADJUSTED SHOWER COVERAGE UP FROM
PREVIOUS FORECAST. SLIGHT TWEAKS MADE TO SKY AND TEMPERATURE TO
ACCOUNT FOR CLOUD COVER OVERNIGHT. DO HAVE THE POSSIBILITY OF
FOG... HOWEVER IT REMAINS IFFY AT THIS TIME... MAY HAVE TO ADJUST
FOR FOG LATER ON.       PROTON

PREVIOUS DISCUSSION...A SIGNIFICANT STORM SYSTEM IS DUE TO ARRIVE THIS
WEEKEND WITH A SOAKING RAIN. WINDY CONDITIONS ARE EXPECTED
SATURDAY.

ANOTHER BAND OF SHOWERS ARE MOVING INTO THE CENTRAL ZONES THIS
AFTERNOON AS DISTURBANCES HAVE PERIODICALLY MOVED NORTHEAST THROUGH
THE AREA. AN UPPER TROUGH WILL DIG TO OUR WEST AS A STRONG
DISTURBANCE DROPS INTO WASHINGTON STATE. THE UPPER LOW WILL CLOSE
OFF OVER THE PACIFIC NW TONIGHT THEN DRIFT THROUGH THE
NORTHERN/CENTRAL ROCKIES FRIDAY AND SATURDAY. THE CLOSED NATURE OF
THIS SYSTEM WOULD FAVOR A SLOWER MODEL SOLUTION.

RAIN SHOWERS SHOULD DISSIPATE EARLY THIS EVENING WITH THE LOSS OF
DAYTIME HEATING. WITH THE SYSTEM CLOSING OFF...NE MT MAY ENJOY A
PERIOD OF RELATIVE DRYNESS THROUGH TOMORROW...ESPECIALLY THE NE
ZONES.

THEN FRIDAY NIGHT AND SATURDAY...THE SYSTEM BEGINS TO THROW A RAIN
SHIELD OUR WAY FROM THE SW. A SOAKING RAIN IS EXPECTED FOR MOST
AREAS SATURDAY BUT PROXIMITY TO A DRY SLOT TO THE SOUTH MAY THROW IN
CONVECTIVE ELEMENTS INTO THE MIX. SINCE SOILS STARTED OUT
RELATIVELY DRY PRIOR TO THIS EVENT...WIDESPREAD FLOODING IS NOT
ANTICIPATED. BUT BRIEF PERIODS OF HEAVY RAIN COULD SWELL
CREEKS/STREAMS. TFJ


.LONG TERM...SATURDAY NIGHT THROUGH THURSDAY...

THE EXTENDED MODELS INITIALLY AGREE WITH GENERAL FEATURES BUT
STILL STRUGGLE WITH DETAILS DUE TO THE DISPLACEMENT OF THE LOW
CENTERS BETWEEN EACH MODEL. THIS IS SIGNIFICANT SINCE IT WILL
DETERMINE WHEN AND WHERE THERE WILL BE RAIN DUE TO THE PLACEMENT
OF THE DRY SINKING AIR BEHIND THE LOW CENTER THAT COULD POSSIBLY
CUT OFF MOST MOISTURE AROUND SUNDAY EVENING. THERE IS ANOTHER
PERIOD NEAR THE END OF NEXT WEEK WHERE THE 00Z MODELS DIFFERED
WITH THE TIMING AND AMPLITUDE WITH THE NEXT TROUGH. HOWEVER BOTH
12Z MODELS CONVERGE ON A MORE SHALLOW LONG WAVE TROUGH BY THURSDAY
EVENING. SCT

FEW CHANGES IN THE EARLY PERIOD SINCE THE RAIN IDEA COMES ACROSS
ELL. ALTHOUGH WITH THE LATEST EC AND NAM...MADE POPS MORE
WIDESPREAD SUNDAY/SUNDAY EVE. LATER IN THE WEEK THE UNCERTAINTY
CONTINUES...THEREFORE FEW OTHER CHANGES WERE MADE. SCT

PREVIOUS DISCUSSION...
STEADY PERIODS OF RAIN CAN BE EXPECTED TO BE ONGOING ACROSS THE
CWA WITH THE UPPER LEVEL TROUGH AXIS DIRECTLY OVER NORTHEAST
MONTANA SATURDAY NIGHT TO START OFF THE EXTENDED PERIOD. 21/00Z
GUIDANCE INDICATES THAT THE LOW WILL CLOSE OFF AS IT TRANSLATES
NORTHEAST ON SUNDAY...ALLOWING THE STEADY RAIN TO TAPER OFF FROM
SOUTHWEST TO NORTHEAST. SREF PLUMES SHOW DECREASING MUCAPE AND
SHEAR THROUGH THE WEEKEND AND SO LEFT OUT MENTION OF THUNDER AS
WRAP AROUND MOISTURE LIFTS OUT OF THE AREA.

MONDAY AND MONDAY NIGHT...AS THE CLOSED LOW PUSHES INTO CENTRAL
SASKATCHEWAN AND MANITOBA...ANOTHER SHORTWAVE APPROACHES IN
NORTHWEST FLOW ALOFT FROM THE PACIFIC NORTHWEST WITH A DEEPENING
TROUGH ONCE AGAIN TO INFLUENCE MONTANA. THERE ARE DIFFERENCES IN
THE WAY THAT THE GFS/ECMWF ARE HANDLING THIS TROUGH...WITH THE
ECMWF HAVING IT FURTHER TO THE WEST AS IT CLOSES OFF A LOW ACROSS
NEVADA. THIS WOULD KEEP PRECIPITATION CHANCES SOUTH OF THE REGION
WHILE THE GFS HAS THE TROUGH DEEPENING OVER MONTANA. WILL SIDE
WITH THE ECMWF FOR NOW AND INTRODUCE A QUIETER PERIOD IN THE WAKE
OF THE WEEKEND SYSTEM AND IN ADVANCE OF THE NEXT.

REGARDLESS...EXPECT NORTHERLY WINDS ON THE BACKSIDE OF THE INITIAL
SYSTEM TO HELP BRING IN UNSEASONABLY COOL TEMPERATURES TO
CONTINUE INTO EARLY NEXT WEEK. IN FACT...SOME PLACES MONDAY
MORNING ALONG THE INTERNATIONAL BORDER AND IN SOME OF THE DEEPER
VALLEY LOCATIONS ALONG THE MILK/MISSOURI RIVER BASINS AND PERHAPS
THE YELLOWSTONE MAY SEE LOW TEMPERATURES DIPPING INTO THE UPPER
30S. THE REALIZATION OF COLDER TEMPERATURES WILL SOMEWHAT DEPEND
ON RADIATIVE COOLING SUNDAY NIGHT AND HOW QUICKLY CLOUDS/
PRECIPITATION EXIT. IF SKIES CAN CLEAR OUT...RADIATIONAL COOLING
WILL MAKE FOR A COLD START FOR MONDAY MORNING AND TEMPERATURES
ONLY RECOVERING TO THE 50S AND 60S DURING THE DAY.

DIFFERENCES IN MODEL SOLUTIONS INCREASE FROM TUESDAY INTO LATE
NEXT WEEK. BOTH GFS AND ECMWF SHOW AN OPPORTUNITY FOR SOME
RIDGING ACROSS NORTHEAST MONTANA TUESDAY INTO WEDNESDAY AND SO
THIS PERIOD MAY OFFER BENIGN WEATHER. RECALL THAT THE GFS HAS A
SECOND TROUGH INITIALLY ACROSS MONTANA ON MONDAY. IT TRACKS THE
TROUGH PROGRESSIVELY FURTHER EAST ALLOWING FOR A RIDGE AND DRY
WEATHER TO PERSIST INTO MUCH OF NEXT WEEK ACROSS THE NORTHERN
PLAINS. IN CONTRAST...THE ECMWF HAS THAT TROUGH FURTHER
WEST...WITH RIDGING OCCURRING OUT AHEAD OF IT WHICH WOULD OFFER
DRY WEATHER FOR TUESDAY AND WEDNESDAY ACROSS THE CWA. THE TROUGH
THEN TRANSLATES EAST WITH A SURFACE LOW TRACKING AHEAD OF IT
DOWNSTREAM LATE NEXT WEEK. PRECIPITATION CHANCES TO THE NORTH OF
THIS LOW WOULD EXTEND FROM WYOMING TO SOUTHEAST MONTANA AND INTO
THE DAKOTAS. IN SHORT...IT IS UNCLEAR WHICH SOLUTION MAY PLAY OUT
AND SO UNCERTAINTY BEYOND MONDAY IS QUITE LARGE. MALIAWCO


&&

.AVIATION...
FLIGHT CATEGORY: IFR TO VFR

SYNOPSIS: A BROAD UPPER LEVEL TROUGH SLOWLY MOVING ACROSS THE
PACIFIC NORTHWEST AND MONTANA WILL BRING INCREASING CHANCES FOR
PRECIPITATION THROUGH THE WEEKEND.

SCATTERED SHOWERS... ISOLATED THUNDERSTORMS... AND LOW LEVEL CLOUD
COVER WILL BECOME MORE WIDESPREAD ACROSS THE AREA. AS A RESULT
TERMINALS WILL EXPERIENCE TEMPORARY MVFR/IFR CEILINGS AND
VISIBILITIES...ALONG WITH GUSTY WIND. OTHERWISE EXPECT OVERCAST TO
BROKEN MID-LEVEL CLOUDS...ALONG WITH LOW CLOUDS THAT INFREQUENTLY
PRODUCE MVFR CEILINGS.

FOG/MIST: IS POSSIBLE BY MORNING...MOST LIKELY AT TAF SITES NEAR
THE YELLOWSTONE RIVER. LIGHT NORTHERLY WINDS ARE EXPECTED THROUGH
FRIDAY MORNING.

AREA WINDS: FROM THE NORTHEAST UNDER 10 KTS OVERNIGHT... VEERING
TO THE EAST AND INCREASING TO 10 TO 15 KTS AFTER SUNUP.

GAH/SCT

&&

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

&&

$$

WEATHER.GOV/GLASGOW





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.