Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 251604 AAA
AFDGGW

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GLASGOW MT
1004 AM MDT MON MAY 25 2015

.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH WEDNESDAY...

SENT AN UPDATE THIS MORNING TO FINE TUNE THE POPS AND WEATHER
GRIDS BASED ON THE LATEST SHORT-TERM AND HI-RES MODEL SOLUTIONS.
THE HRRR MODEL IS SHOWING A BIT MORE CONVECTIVE ACTIVITY HAPPENING
TODAY THAN YESTERDAY. CHOSE TO INCLUDE SPRINKLES FOR LESS THAN
SLIGHT CHANCE POPS. THUNDERSTORMS SHOULD BE ISOLATED OR SCATTERED
AT BEST THIS AFTERNOON. WINDS OVERALL WITH BE LIGHT AND VARIABLE
WITH A BIT MORE GUSTY NEAR THE STRONGER STORMS...WHICH SHOULD BE
CONFINED TO OUR SOUTHERN AND SOUTHEASTERN ZONES. BMICKELSON

THE LATEST 00Z MODEL GUIDANCE CONTINUES TO KEEP MOST RAIN CHANCES
TO THE SOUTH OF THE MISSOURI RIVER FOR TODAY AND THIS IDEA MATCHES
UP WELL WITH CURRENT RADAR OBSERVATIONS...WITH REFLECTIVITY ECHOES
APPARENT OVER THE SOUTHERN ZONES VERY EARLY THIS MORNING.

AN UPPER LOW OVER THE PACIFIC NORTHWEST WILL GRADUALLY TRANSLATE
EAST AND PROVIDE INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS
ON TUESDAY AND ESPECIALLY ON WEDNESDAY. THE 00Z NAM BUFKIT
SOUNDINGS SHOW PRECIPITABLE WATER VALUES EXCEEDING AN INCH ACROSS
PORTIONS OF THE CWA...APPROACHING +2SD.

A NEARLY SATURATED VERTICAL COLUMN WEDNESDAY AFTERNOON IS
SUGGESTIVE OF GREATER COVERAGE. ADDITIONALLY...LITTLE CIN AND
LOOKS LIKE 500 J/KG OF CAPE AS WELL IN THE PRESENCE OF SOME
DIRECTIONAL WIND SHEAR BUT NOT MUCH SPEED SHEAR IN THE 0-6 KM
LAYER. LIFTED INDEX VALUES SHOULD BE NEAR 0. THE CWA WILL ALSO BE
ON THE NORTHERN PERIPHERY OF A SUBTLE THETA-E RIDGE DURING THIS
TIME PERIOD AS THE SHORTWAVE TROUGH APPROACHES FROM WESTERN AND
CENTRAL MONTANA...HELPING TO ENHANCE DYNAMIC FORCING FOR ASCENT.
DAYTIME HIGH TEMPERATURES IN THE 70S AND SURFACE DEW POINTS IN THE
LOWER TO MID 50S ARE REFLECTIVE OF THE WARM AND MOIST ENVIRONMENT
SO FEEL PRETTY GOOD ABOUT SHOWER/THUNDERSTORMS MENTIONED IN THE
CURRENT FORECAST.

SPC PAINTS A MARGINAL RISK ACROSS WESTERN SOUTH DAKOTA...WELL TO
THE SOUTHEAST OF THE CWA. GIVEN THE CONVECTIVE PARAMETERS
DISCUSSED THOUGH WOULD NOT BE SURPRISED TO SEE A FEW PLACES SEE SOME
SMALL HAIL OR BRIEF GUSTY WINDS...WITH INCREASING CHANCES FURTHER
TO THE SOUTHEAST. PROXIMITY TO THE TROUGH COULD MEAN HIGHER
CONCENTRATIONS OF CLOUD COVER THOUGH WHICH WOULD INHIBIT SOLAR
INSOLATION AND LIMIT STRENGTH OF CONVECTION AND THAT IS A FACTOR
TO BE CONSIDERED. NEVERTHELESS DO EXPECT SHOWERS AND GENERAL
THUNDERSTORMS WITH THIS DESCRIBED SETUP...AND A FEW COULD
CERTAINLY PRODUCE BRIEF STEADY/HEAVY RAINFALL GIVEN HIGH
PRECIPITABLE WATER IN THE VERTICAL COLUMN. MALIAWCO

.LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY...

PERIOD STARTS OUT WITH AN AN UPPER TROUGH ACROSS MONTANA THURSDAY
AND THURSDAY NIGHT. MODELS DIFFER ON HOW QUICKLY THIS TROUGH WILL
SPLIT. GFS GENERALLY SPLITS THE TROUGH AND TAKES IT TO THE SOUTH
BEFORE IT REACHES EASTERN MONTANA WHILE THE ECMWF WAITS UNTIL THE
SYSTEM UNTIL IT REACHES NORTH DAKOTA. MEANWHILE...THEY AGREE ON A
COLD FRONT THURSDAY NIGHT AND GENERATE SOME PRECIP WITH IT. WILL
MENTION A CHANCE OF SHOWERS AND THUNDERSTORMS.

HIGH PRESSURE BUILDS INTO NORTH DAKOTA THURSDAY NIGHT AND FRIDAY
WHICH WILL BRING MAINLY DRY WEATHER TO THE NORTHEAST HALF OF THE
FORECAST AREA. MEANWHILE...IT LOOKS LIKE THE FRONT COULD STALL
OVER CENTRAL MONTANA. WILL MAINTAIN A SLIGHT CHANCE OF SHOWERS AND
THUNDERSTORMS AT TIMES IN THE SOUTHWEST.

AFTER A SHORTWAVE RIDGE MOVES THROUGH EASTERN MONTANA FRIDAY
NIGHT... THE FRONT MOVES BACK EAST AS A WARM FRONT ON SATURDAY.
A SHORTWAVE TROUGH AND COLD FRONT SATURDAY NIGHT AND SUNDAY COULD
BRING AT LEAST A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS.

ANOTHER SHORTWAVE TROUGH IN NEARLY ZONAL FLOW ALOFT COULD BRING
ANOTHER CHANCE OF SHOWERS NEXT MONDAY. FORRESTER

&&

.AVIATION...

MOSTLY VFR.

RAIN SHOWERS AND MVFR/IFR CONDITIONS ARE EXPECTED TO REMAIN SOUTH
AND EAST OF KGDV TODAY.

WINDS: LIGHT SOUTHEAST BECOMING LIGHT AND VARIABLE TONIGHT.

&&

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

&&

$$

WEATHER.GOV/GLASGOW





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