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000
FXUS65 KGGW 191520 AAA
AFDGGW

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GLASGOW MT
920 AM MDT SUN MAY 19 2013

.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH TUESDAY...
THE LOW PRESSURE CENTERS ARE CLOSING OFF AND BEGINNING TO STACK
OVER THE WESTERN DAKOTAS WHERE THE FOCUS OF PRECIPITATION IS THIS
MORNING. A BIT OF DRY SLOTTING THROUGH THE CENTRAL COUNTIES OF
NORTHEAST MONTANA PROMPTED SOME ADJUSTMENTS TO POPS/QPF AND WX FOR
TODAY. EXPECT WIND TO PICK UP AS THE SURFACE LOW RETROGRADES BACK
TOWARDS OUR CWA. AS IT DOES THE INVERTED SURFACE TROUGH NUDGES
INTO NEMONT BRINGING HEAVIER RAIN AND SOME THUNDERSTORMS BY LATE
AFTERNOON. ADJUSTED WIND BASED ON OBSERVATIONS AND THE LATEST
GUIDANCE. TEMPERATURES LOOK GOOD SO NO ADJUSTMENTS THERE. SCT

PREVIOUS DISCUSSION...
TODAY THROUGH MONDAY NIGHT...UPPER LEVEL TROUGH WILL CONTINUE TO
PROVIDE UNSETTLED WEATHER CONDITIONS FOR NE MT. A SURFACE LOW
PRESSURE SYSTEM WILL CONTINUE TO SIT AND SPIN AS IT BECOMES
VERTICALLY STACKED OVER EASTERN SOUTH DAKOTA BY MONDAY. THIS LOW
PRESSURE WILL CONTINUE TO PUMP EASTERLY SURFACE FLOW INTO THE CWA
WHICH WITH COMBINED WITH LOBES OF UPPER LEVEL SHORTWAVE ENERGY
SWIRLING AROUND THE TROUGH...WILL HELP PROVIDE THE SUPPORT FOR A
CONTINUATION OF VERY STEADY RAIN SHOWERS. LOOKING AT NAM BUFR
FORECAST SOUNDINGS...DO NOTE THAT LI IS NEAR 0 IN SOME LOCATIONS
DURING SUNDAY AFTERNOON WITH TOTAL TOTALS HOVERING AROUND 50.
GIVEN THE CONVECTIVE NATURE OF THE PULSES OF SHOWER ACTIVITY THAT
HAVE OCCURRED THE PAST COUPLE OF DAYS HOWEVER...AM NOT COMPLETELY
SOLD ON THE IDEA THAT THUNDER WILL NOT AT ALL BE A POSSIBILITY.
WITH THE STEADY RAINS...DO FEEL EMBEDDED THUNDER IS A POSSIBILITY
AND SO KEPT IN A SLIGHT MENTION OF IT. SOUNDINGS ARE ALSO SHOWING
AN INCH OR MORE PRECIPITABLE WATER THROUGH THIS PERIOD AND SO
THERE IS CERTAINLY PLENTY OF MOISTURE IN THE VERTICAL TO WORK
WITH.

MODEL GUIDANCE HAS BEEN FAIRLY CONSISTENT WITH THE STEADY
RAINS AFFECTING MUCH OF THE CWA THROUGH MONDAY NIGHT...BUT
PREFERRED THE ECMWF AND THE HRRR SOLUTIONS GIVEN EXCELLENT RUN TO
RUN CONTINUITY. WILL EXPECT THE HEAVIEST RAINFALL AMOUNTS IN THE
SOUTHEASTERN ZONES CLOSER TO THE SURFACE LOW...BUT ISOLATED HIGHER
RAINFALL TOTALS MAY OCCUR WHERE THUNDER AND/OR THE STEADIEST
RAINFALL DOES OCCUR. THAT WILL LARGELY DEPEND UPON MESOSCALE
DETAILS THAT ARE COMPLEX AND DIFFICULT TO PINPOINT AT THIS TIME.
CERTAINLY THERE WILL LIKELY BE A WIDESPREAD WETTING RAIN ACROSS
THE CWA THROUGH MONDAY NIGHT...BUT ISOLATED LOCATIONS MAY PICK UP
AN ADDITIONAL ONE TO TWO INCHES OF RAINFALL.

TUESDAY...THE RAIN SLOWLY EXITS THE FORECAST REGION FROM WEST TO
EAST. HAVE DROPPED OFF POPS ACCORDINGLY DURING THE DAY ON TUESDAY
AND ESPECIALLY TUESDAY NIGHT. WITH LITTLE CHANGE IN THE FORECAST
850MB TEMPERATURES...WILL NOT EXPECT MUCH IN THE WAY OF SWINGS.
EXPECTING SEASONAL CONDITIONS THROUGH THE ENTIRE SHORT TERM
PERIOD...OR PERHAPS SLIGHTLY BELOW AVERAGE WITH THE LARGE TROUGH
IN PLACE. MALIAWCO


.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...
THE EXTENDED PERIOD CONTINUES WITH UPPER LOWS TO OUR WEST AND EAST
AND CONFUSED FLOW OVER NORTHEAST MONTANA. THIS WILL CONTINUE UNTIL
FRIDAY WHEN THE UPPER LOW IN THE PACIFIC NORTHWEST SHIFTS CLOSER
TO NORTHEAST MONTANA. THIS WILL ENHANCE THE POSSIBILITY OF
THUNDERSTORMS OVER THE WEEKEND.

TEMPERATURES WILL CONTINUE AROUND NORMAL WITH HIGHS HOVERING
AROUND 70 AND LOWS IN THE UPPER 40S TO LOWER 50S THROUGH THE PERIOD.

MODEL TRENDS SHOW A FAIRLY SMOOTH RUN TO RUN PERFORMANCE WHICH
ASSISTS WITH A HIGH CONFIDENCE. DID NOT GO TOO HIGH FOR POPS OVER
THE UPCOMING WEEKEND SINCE THERE IS A HINT OF RETROGRESSION
STARTING TO SHOW UP WITH FALLING HEIGHTS IN MOST ENSEMBLES OVER
THE NORTHEAST PACIFIC. THIS COULD LEAD TO THE UPPER LOW SINKING
FURTHER SOUTH AND WEST KEEPING NORTHEAST MONTANA DRIER. OVERALL
ENSEMBLES ARE FAIRLY GOOD SINCE WE ARE IN A CLIMATOLOGICAL NORMAL
PATTERN. RMOP ARE FAIRLY GOOD WITH THE LARGE SCALE FEATURES FOR
THE EXTENDED PERIOD. THEREFORE MODERATE TO GOOD CONFIDENCE IN THE
PERIOD FROM TUESDAY NIGHT THROUGH FRIDAY WITH SOME LOWER
CONFIDENCE IN THE WEEKEND PATTERN.            PROTON

&&

.AVIATION...
MVFR. MODELS HAVE BEEN A LITTLE LOW ON CEILING HEIGHTS AT ALL
LOCATIONS FOR PAST 48 HOURS AND LOOK TO CONTINUE THE TREND FOR THE
NEXT 24 HOURS. WILL MAINTAIN MVFR AT MOST LOCATIONS WITH LOW VFR
FOR GLASGOW THROUGH THE PERIOD. COOLER TEMPERATURES ALOFT WILL
CONTINUE THE SHOWERY CONDITIONS THROUGH THE PERIOD.        PROTON

&&

.HYDROLOGY...
THE NEXT FEW DAYS WILL BE RATHER WET AS AN UPPER-LEVEL TROUGH
AFFECTS THE AREA. SEVERAL DISTURBANCES ASSOCIATED WITH THIS
TROUGH WILL PASS THROUGH WHICH WILL KEEP CHANCES FOR RAIN WITH
SOME THUNDERSTORMS THROUGH EARLY NEXT WEEK. MODEL GUIDANCE DEPICTS
HIGH AMOUNTS OF MOISTURE WITH THIS SYSTEM. AT THIS POINT THE
ENVIRONMENT LOOKS FAVORABLE FOR SLOW-MOVING STORMS WITH HIGHER
PRECIPITATION IN LOCALIZED AREAS.

MOST OF THE BASINS IN NORTHEAST MONTANA WILL BE ABLE TO
ACCOMMODATE THIS AMOUNT OF MOISTURE...AT LEAST EARLY ON IN THE
EVENT. THERE IS SOME CONCERN FOR RAPIDLY RISING STREAMS...FIELD
FLOODING AND LOCALIZED FLOODING IN TOWNS AS THE EVENT PERSISTS.
SOME MINOR FLOODING MAY BECOME AN ISSUE... ESPECIALLY FOR THE
AREAS FROM GLASGOW TO CIRCLE AND EASTWARD INTO NORTH DAKOTA WHERE
THE POTENTIAL FOR STRONGER THUNDERSTORMS IS HIGHER.


&&

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

&&

$$

WEATHER.GOV/GLASGOW