Area Forecast Discussion
Issued by NWS Glasgow, MT

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000
FXUS65 KGGW 242042
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
242 PM MDT SUN MAY 24 2015

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

CYCLONIC FLOW ALOFT WILL CONTINUE OVER THE LOWER YELLOWSTONE
VALLEY TONIGHT INTO MONDAY AS AN UPPER LOW CURRENTLY CENTERED OVER
NORTHERN COLORADO LIFTS INTO WYOMING AND SOUTH DAKOTA. MODELS CONTINUE
TO STRUGGLE WITH THE EXACT PLACEMENT OF PRECIP...BUT THE CONSENSUS
SEEMS REASONABLE...KEEPING ANY SIGNIFICANT RAIN SHOWER ACTIVITY
LIMITED TO THE LOWER YELLOWSTONE VALLEY...MAINLY TERRY...WIBAUX...AND
GLENDIVE.

MONDAY AFTERNOON DECENT INSTABILITY LOOKS TO BE PRESENT ACROSS
MOST OF NORTHEAST MONTANA...HOWEVER SHEAR AND A TRIGGER LOOK TO BE
ABSENT OR LACKING. THUS EXPECT ISOLATED TO SCATTERED SHOWERS AND
THUNDERSTORMS TO DEVELOP DURING THE AFTERNOON HOURS...AGAIN WITH
THE BEST THREAT FALLING ACROSS THE FAR SOUTHEAST...INCLUDING
WIBAUX...TERRY...GLENDIVE...AND SIDNEY.

MONDAY EVENING THE THREAT FOR THUNDERSTORMS WILL TAPER OFF DURING
THE EVENING HOURS...WHILE THE THREAT FOR ISOLATED SHOWERS LINGERS
OVERNIGHT INTO TUESDAY. GILCHRIST


.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...

AS THIS SECONDARY CLOSED UPPER LOW CENTER SWEEPS THROUGH THE
PACIFIC NORTHWEST AND HEADS TOWARD NE MONTANA BY MID WEEK...IT
LOSES MUCH OF ITS STRENGTH AND BECOMES ABSORBED INTO THE LARGER-
SCALE NORTHERN STREAM TROUGH PINWHEELING AROUND THE HUDSON BAY
LOW.

FELT I COULD ADD ONLY MINIMAL UPDATES TO THE GOING EXTENDED
FORECAST THROUGH WEDNESDAY NIGHT. SMALLER-SCALE MODEL
DISCREPANCIES REGARDING PRECIP TIMING AND PLACEMENT STILL REMAIN
FAR OUT OF AGREEMENT TO EVEN BEGIN TO ADJUST WITH ANY CONFIDENCE.
GENERALLY SPEAKING...WHILE THE OVERALL LARGE-SCALE SYNOPTIC
PATTERN SHOWS FAIRLY GOOD MODEL AGREEMENT WITH A WEDNESDAY MORNING
THROUGH FRIDAY MORNING WET PERIOD...EXACTLY HOW THAT TRANSLATES
TO HOW MUCH PRECIP AT THE SURFACE IS STILL QUITE A BIT MUDDLED AT
THIS TIME WITH POORER SMALL SCALE MODEL AGREEMENT. BMICKELSON

THERE IS FAIRLY DECENT 00Z MODEL AGREEMENT IN THE EXTENDED PERIOD
WHICH BEGINS TUESDAY NIGHT WITH AN UPPER TROUGH...WHICH WILL
GRADUALLY TRANSLATE EAST ACROSS THE NORTHERN HIGH PLAINS THROUGH
THE MIDWEEK. THIS TROUGH WILL MAINTAIN UPPER FORCING FOR ISOLATED
TO SCATTERED SHOWERS AND THUNDERSTORMS THROUGH THE PERIOD.

A SURFACE COLD FRONT LOOKS TO PUSH THROUGH THE REGION SOMETIME ON
THURSDAY. THE 00Z GFS AND ECMWF KEEP BEST CHANCES FOR SHOWER
ACTIVITY ON THE PERIPHERY OF THE CWA...BUT GIVEN THAT IT IS DAY 5
AND THE POTENTIAL FOR SOME ENHANCED SURFACE CONVERGENCE ALONG THE
COLD FRONT...WILL KEEP AT LEAST A SLIGHT CHANCE IN CENTRAL ZONES
FOR NOW.

WILL TREND TOWARD A DRY FORECAST FOR THE WEEKEND AS COMPARED WITH
PREVIOUS FORECASTS. LATEST GUIDANCE NOW SHOWS MORE AGREEABLE
SUPPORT FOR AN UPPER RIDGE BUILDING ACROSS THE WESTERN CONUS. THIS
WILL INEVITABLY LEAD TO RISING 1000-500 MB THICKNESSES ACROSS THE
AREA AND THUS WARMER TEMPERATURES. THE 00Z ECMWF 850MB
TEMPERATURES LOOK TO RANGE NEAR +20C OVER THE CWA BY 01 JUNE.
WHILE IT IS VERY PRELIMINARY THINKING...EARLY INDICATIONS ARE THAT
JUNE MAY START OUT ON A WARMER NOTE. WILL SEE IF FUTURE MODEL RUNS
OFFER SIMILAR SOLUTIONS...WHICH WOULD HELP TO BUILD CONFIDENCE.
FOR NOW WILL KEEP A DRY FORECAST AND WARMER TEMPERATURES TO FINISH
OUT THE EXTENDED PERIOD. MALIAWCO

&&

.AVIATION...
FLIGHT CATEGORY AT KOLF AND KGGW...VFR.

FLIGHT CATEGORY AT KSDY AND KGDV...VFR TO MVFR.

SYNOPSIS: AN UPPER LOW PASSING TO THE SOUTHEAST WILL DRIVE
SCATTERED TO WIDESPREAD SHOWERS AND THUNDERSTORMS...MAINLY TARGETED
OVER THE LOWER YELLOWSTONE VALLEY TODAY INTO MONDAY. FURTHER NORTH
AND WEST...KOLF AND KGGW WILL SEE LESSER IMPACTS FROM THE
LOW...WITH MAINLY SCT-BKN MID AND HIGH CLOUDS EXPECTED. WITH THAT
SAID CAN NOT RULE OUT AN ISOLATED MVFR TO IFR THUNDERSTORM AT ANY
TERMINAL ON MONDAY.

WINDS: EAST 5-15KTS.

GILCHRIST


&&

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

&&

$$

WEATHER.GOV/GLASGOW





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