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 180834
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
234 AM MDT THU SEP 18 2014

.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH SATURDAY...
UPPER RIDGE WILL BE FLATTENED TODAY BY A WEAK SHORTWAVE MOVING
ACROSS MONTANA. THIS WAVE WILL INTERACT WITH A WARM AND UNSTABLE
AIRMASS TO PRODUCE A FEW THUNDERSTORMS MAINLY THIS AFTERNOON AND
EVENING. A THERMAL RIDGE WILL ALLOW TEMPERATURES TO RISE INTO THE
80S IN MOST AREAS... MAY SEE AN ISOLATED 90 DEGREE HIGH IN THE SOUTH.

A COLD FRONT LATE TONIGHT AND FRIDAY MORNING ALONG WITH A
SHORTWAVE TROUGH ON ZONAL FLOW ALOFT WILL BRING A SLIGHT CHANCE OF
SHOWERS AND THUNDERSTORMS TONIGHT AND FRIDAY. NORTHWEST WINDS MAY
BE STRONG ENOUGH ON FRIDAY FOR A LAKE WIND ADVISORY ON FORT PECK
LAKE.

NORTHWEST FLOW ALOFT WILL BRING COOLER TEMPERATURES ON SATURDAY AS
A HIGH PRESSURE SYSTEM BUILDS INTO THE AREA WITH DRY WEATHER. FORRESTER


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

THERE SEEM TO BE THREE DIFFERENT FEATURES INTERACTING WITH EACH
OTHER THROUGH THE EXTENDED FORECAST PERIOD. FIRST IS THE RIDGE OF
HIGH PRESSURE. NEXT IS THE WEAK CLOSED LOW OR AREA OF WEAK LOW
PRESSURE UNDER THE RIDGE. THE THIRD IS THE LARGE LOW PRESSURE
TROUGH OFF THE WEST COAST OF U S AND CANADA.

MODEL AGREEMENT IS NEAR PERFECT FROM SATURDAY NIGHT THROUGH MONDAY
AFTERNOON KEEPING THE RIDGE OF HIGH PRESSURE OVER THE NORTHERN
HIGH PLAINS AND KEEPING OUR TEMPERATURES WARM AND WEATHER
CONDITIONS DRY.

STARTING MONDAY NIGHT...MODELS BEGIN TO SHOW SOME SLIGHT
DISAGREEMENTS. THE AREA OF WEAK LOW PRESSURE UNDER THE RIDGE VERY
SLOWLY EMERGES FROM THE CENTRAL ROCKIES TO OVER THE NORTHERN HIGH
PLAINS...BUT AS IT DOES SO...THE GFS DISSOLVES IT NEARLY
COMPLETELY EAST OF US BY WEDNESDAY MORNING WHILE THE EC MAINTAINS
IT AND PULLS IT DIRECTLY THROUGH NORTHEAST MONTANA THROUGH
WEDNESDAY AFTERNOON. CONSEQUENTLY...AS THIS MOISTURE APPROACHES
FROM THE SOUTHWEST...THE EC SHOWS A WETTER FORECAST FOR TUESDAY
NIGHT THROUGH WEDNESDAY WHILE THE GFS KEEPS THING DRY. AS THE
DISTURBANCE IS OVERALL WEAK...CHOSE TO BLEND THE TWO CAMPS HERE
AND KEEP THE FORECAST DRY WITH SUB-SLIGHT CHANCE POPS UNTIL
MODELS COME INTO BETTER AGREEMENT.

LASTLY...THE CHAOS ENSUES BEGINNING THURSDAY MORNING AS THE MODELS
TRY TO DEPICT SOME KIND OF PATTERN CHANGE AND LOW PRESSURE STORM
SYSTEM DIVING DOWN FROM THE CANADIAN ROCKIES. CHOSE TO INTRODUCE
SOME BROAD-BRUSHED SLIGHT CHANCE POPS GIVEN THE LIKELIHOOD OF THE
OVERALL PATTERN CHANGE...BUT DETAILS ARE OBVIOUSLY STILL
FORTHCOMING. THE GFS BRINGS DOWN A LARGE AND LONG-WAVE TROUGH
WHILE THE EC KEEPS A MORE NARROW TROUGH...EVENTUALLY CLOSING OFF
AN UPPER LOW AND SEPARATING FROM THE NORTHERN STREAM. WE WILL
LIKELY SEE SOME KIND OF A STRONG COLD FRONTAL SYSTEM APPROACHING
THE REGION BY THIS TIME NEXT WEEK. BMICKELSON

&&

.AVIATION...

SYNOPSIS: THE UPPER-LEVEL RIDGE CREST IS CURRENTLY BEING MUTED OR
FLATTENED BY AN APPROACHING UPPER-LEVEL TROUGH FROM THE WEST. BUT
THERE WILL BE ENOUGH OF A WARMING EFFECT REMAINING UNDER THE
WEAKENING RIDGE TO ALLOW TEMPERATURES TO FLIRT WITH THE 90 DEGREE
MARK TODAY. ENOUGH INSTABILITY WILL BE PRESENT TO SET OFF SOME
CONVECTIVE RAIN SHOWERS AND A FEW THUNDERSTORMS DURING THE
AFTERNOON AND EVENING HOURS.

FLIGHT CATEGORY: VFR CONDITIONS WILL PREVAIL FOR ALL TAF SITES
THROUGHOUT MOST OF THE TAF CYCLE. SOME VICINITY SHOWERS COULD
IMPACT THE AREA AROUND KGDV...AND AMENDMENTS MIGHT BE NEEDED IF A
STRONGER STORM APPROACHES DURING THE AFTERNOON AND EVENING HOURS
WHICH COULD BRING PERIODS OF BRIEF IFR CONDITIONS.

AREA WINDS: CALM OR LIGHT EARLY...BECOMING BREEZY FROM THE
SOUTHWEST DURING THE WARMEST PART OF THE DAY. WINDS COULD BE GUSTY
AND ERRATIC NEAR KGDV WITH ANY PASSING STORMS. WINDS WILL THEN
GENERALLY RETURN TO LIGHT FROM THE WEST OR CALM AFTER SUNSET.
BMICKELSON




&&

.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.