Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 280212
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
812 PM MDT WED MAY 27 2015

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH FRIDAY...

EVENING UPDATE...
CHANGES THIS EVENING WERE MINOR BUT ENCOMPASSED A LOT OF AREAS.
FIRST LOW PRESSURE CENTERED OVER NORTHERN VALLEY COUNTY WILL
PROVIDE LIMITED LIFT ALL EVENING FOR RAIN SHOWERS ACROSS MOST OF
THE AREA WITH THE EXCEPTION OF THE YELLOWSTONE VALLEY. POPS WERE
TWEAKED TO ADDRESS THIS. WITH RAIN SHOWERS ONGOING FROM THE
AFTERNOON INTO LATE EVENING CLEARING DURING THE OVERNIGHT HOURS
WILL COMBINE WITH EXCESS MOISTURE TO PRODUCE PATCHY FOG ACROSS
SOME OF THE AREA WITH A FOCUS ON THE NORTHEAST SECTIONS OF THE CWA
INCLUDING SHERIDAN... ROOSEVELT... AND DANIELS COUNTY. PEAK TIME
WILL PROBABLY BE BETWEEN 3 AND 9 AM. WINDS AND QPF WERE ALSO
TWEAKED SLIGHTLY TO ACCOUNT FOR THIS. GAH


PREVIOUS SHORT TERM DISCUSSION...
UPPER LOW OVER THE NORTHERN ROCKIES HAS OPENED UP AND ALLOWED A
WEAK DISTURBANCE TO FOCUS THUNDERSTORMS OVER EASTERN MONTANA
TODAY. SOME WERE STRONG THAT WENT THROUGH THE GLENDIVE
AREA...BRINGING BRIEF HEAVY RAIN AND PEA-SIZE HAIL.

FOCUS THROUGH THIS EVENING IS SHOWER/TSTORM ACTIVITY. ACTIVITY
OVER THE SOUTHEAST ZONES SHOULD BE ABSORBED BY A CONVECTIVE
CLUSTER OVER WESTERN NORTH DAKOTA. BUT IT COULD LINGER LONGER THAN
EXPECTED WITH IT FINALLY EXITING THE NORTHEAST ZONES AROUND
MIDNIGHT. SCATTERED THUNDERSTORMS OVER CENTRAL MONTANA AND THE SW
ZONES WILL CONTINUE DRIFTING ENE BUT WITH MOISTURE NOT BEING AS
DEEP IN THE AREA...THEY SHOULD DISSIPATE THIS EVENING.

OTHERWISE...UPPER LOW REMNANTS GRADUALLY PUSHES TO OUR SOUTHEAST
TOMORROW NIGHT AS ATTENTION TURNS TO A COLD FRONT THAT PUNCHES
IN FROM THE NORTH. MAIN CONCERN WITH THIS WILL BE THE WINDS.
MODELS SHOWING A QUICK INCREASE IN NORTH WINDS WITH GUSTS TO 30 MPH.
WILL HOLD OFF ON LAKE WIND ADVISORY FOR NOW BUT WILL HIGHLIGHT IN
AN HWO AND BRIEF LATER SHIFTS ON THIS.

THURSDAY NIGHT AND FRIDAY...A DRY AND COOL AIRMASS MOVES IN WITH
TEMPERATURES FALLING INTO THE UPPER 30S ACROSS THE NORTHERN ZONES.
SUNSHINE ON FRIDAY SHOULD ALLOW TEMPS TO REBOUND INTO THE 60S
MOST PLACES. TFJ


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

MADE SOME ADJUSTMENTS TO THE EXTENDED FORECAST PERIOD THROUGH
TUESDAY MORNING. ENSEMBLE SPREAD IN THE GFS SHOWS QUITE GOOD
AGREEMENT FOR NE MONTANA THROUGH MOST OF THIS FORECAST PERIOD.
WHEN PRECIP OUTPUT MODEL CONSENSUS FELL COMPLETELY APART...DID NOT
ADJUST BEYOND THAT TIME FRAME.

EXTENDED FORECAST PERIOD BEGINS WITH BROAD WEAK RIDGING OVER THE
NORTHERN ROCKIES AND NORTHERN HIGH PLAINS WHICH QUICKLY BECOMES A
ZONAL FLOW ALOFT BY SATURDAY AFTERNOON. NO PRECIP EXPECTED.

SATURDAY AFTERNOON SHOULD SEE A RETURN TO SOME LIGHT SCATTERED
RAIN SHOWERS AS AN UPPER LOW FROM BRITISH COLUMBIA BEGINS TO CUT
INTO THAT ZONAL FLOW FROM THE NORTH JUST A BIT. MAYBE A FEW
THUNDERSTORMS.

OF GREATER INTEREST IS THE MONDAY EVENING THROUGH WEDNESDAY NIGHT
TIME FRAME WHEN THE LARGER UPPER-LEVEL TROUGH OFF THE CENTRAL WEST
COAST MOVES INLAND AND PUSHES OVER THE IDAHO/MONTANA BORDER.
MODELS CONTINUE TO INDICATE THAT THIS WILL BE AN ACTIVE WEATHER
PATTERN WITH STRONGER THUNDERSTORMS POSSIBLE. ANY DETAILS BEYOND
GENERAL FLOW ARE TOO FAR OUT TO PIN DOWN YET...BUT IT WARRANTS A
CLOSE EYE FOR MODEL CONSISTENCY AND POSSIBLE MENTION IN FUTURE HWO
AND SOCIAL MEDIA. BMICKELSON


PREVIOUS LONG TERM DISCUSSION...
THE EXTENDED PERIOD WILL GET STARTED FRIDAY NIGHT WITH A CLOSED
UPPER LOW OVER SOUTHERN BRITISH COLUMBIA WITH ZONAL FLOW ALOFT
COMING IN TO THE SOUTH FROM THE PACIFIC NORTHWEST PUSHING INTO THE
NORTHERN HIGH PLAINS. THE CLOSED LOW WILL TRANSITION INTO AN OPEN
WAVE AS IT SLIDES EAST AND AN UPPER RIDGE LOOKS TO BUILD INTO THE
WESTERN CONUS. WITH THE CWA ON THE NORTHERN PERIPHERY OF THE RIDGE
AND SOUTHERN INFLUENCE FROM THAT UPPER LOW THERE IS ROOM FOR
SLIGHT CHANCES FOR SHOWERS AND THUNDERSTORMS THROUGH THE WEEKEND.
THE UPPER RIDGE WILL ALSO BRING RISING HEIGHTS AND LEAD TO WARMER
TEMPERATURES. THE LATEST ECMWF HAS +20C 850MB TEMPERATURES ACROSS
THE SOUTHWEST ZONES BY SUNDAY AFTERNOON. GIVEN THESE ARGUMENTS
WILL HAVE HIGHS REACHING THE MID AND UPPER 70S NEAR THE NORTH
DAKOTA BORDER AND MID 80S FURTHER TO THE SOUTHWEST.

MONDAY AND TUESDAY OF NEXT WEEK...A NEW PACIFIC TROUGH WILL
APPROACH FROM THE WEST PROVIDING DIFFLUENT UPPER SOUTHWEST FLOW
OVER THE NORTHERN HIGH PLAINS. THIS ENERGETIC SYSTEM WILL LIKELY
PUMP IN PACIFIC MOISTURE AND SO SEE NO REASON NOT TO CARRY CHANCE
POPS TO FINISH OUT THE EXTENDED AS SHOWERS AND THUNDERSTORMS LOOK
VERY REASONABLE. A FEW STRONGER STORMS MAY BE POSSIBLE WITH THIS
SORT OF SETUP BUT THAT PICTURE WILL BECOME MORE CLEAR AS THIS
FEATURE APPROACHES THE SHORT TERM. THERE IS STILL PLENTY OF MODEL
SPREAD THIS FAR OUT INTO THE LONG RANGE...MAKING IT DIFFICULT TO
OFFER MUCH DETAIL WITH ANY CONFIDENCE. MALIAWCO


&&

.AVIATION...
AN ISOLATED SHOWER AND THUNDERSTORM REMAINS POSSIBLE OVERNIGHT.
TAF SITES CAN ALSO EXPECT SOME PATCHY FOG AFTER 06Z IF SKY
CONDITIONS CLEAR OUT. WHILE VFR CONDITIONS WILL PREVAIL...LOWER
CIGS AND RESTRICTED VSBYS MAY ACCOMPANY ANY SHOWER ACTIVITY AND/OR
FOG THAT OCCURS. WINDS ARE EXPECTED TO BE LIGHT AND VARIABLE
OVERNIGHT OR IF ANYTHING LIGHT OUT OF THE EAST. MALIAWCO


&&

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


&&

$$

WEATHER.GOV/GLASGOW




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