Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 300212
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
812 PM MDT MON SEP 29 2014

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


EVENING UPDATE...
CHANGES FOR THIS EVENING WERE FOCUSED ON REDUCING POPS THROUGH
MIDNIGHT AND QPF TOTALS THROUGH 6AM. RADAR TRENDS ARE SHOWING
ALMOST NOTHING ACROSS THE CWA AND MODEL DO NOT BRING RAIN TO THE
CWA UNTIL AFTER MIDNIGHT. WHEN HIGH RESOLUTION MESOSCALE MODELS ARE
FACTORED INTO QPF... THE TOTALS FOR THE BEGINNING OF THE
MORNING WAVE ARE REDUCED SUBSTANTIALLY. WINDS AND SKY FIELDS WERE
ALSO TWEAKED SLIGHTLY TO HELP KEEP TAF FORECASTS CONSISTENT WITH
THE PUBLIC SIDE. GAH


PREVIOUS SHORT TERM DISCUSSION...
A COOL AND WET PATTERN HAS SET UP OVER THE REGION WITH THE
EXIT OF A TROUGH INTO THE NORTHERN PLAINS/UPPER MIDWEST AND A
TROUGH LIFTING NORTH-NORTHEAST OVER THE INTER-MOUNTAIN STATES.
CURRENTLY...THE SURFACE TROUGH AXIS EXTENDS SOUTHEAST FROM THE LOW
OVER CENTRAL ALBERTA TO THE LOW OVER CENTRAL WYOMING WITH THE BULK
OF THE PRECIPITATION OCCURRING OVER WESTERN SOUTH
DAKOTA...SOUTHWEST NORTH DAKOTA AND PORTIONS OF NORTHEAST MONTANA.
PATCHY FOG HAS BEEN OBSERVED OFF AND ON TODAY WITH THE RAIN
SHOWERS ACROSS THE AREA.

TONIGHT THROUGH TUESDAY...THE SURFACE LOW WILL SLOWLY MIGRATE
NORTH...TRANSFERRING MORE MOISTURE OVER THE DEFORMATION AXIS ACROSS
THE EASTERN MONTANA AND SLOWLY MORPH IT INTO A TROWAL AS THE LOW
TRAINS INTO THE DAKOTAS. PATCHY FOG MAY BE OBSERVED ALONG WITH THE
RAIN DURING THE OVERNIGHT HOURS. MEANWHILE...THE RIDGE FROM THE
NORTHWEST WILL BEGIN EXERTING INFLUENCE BY THE EVENING HOURS AND
PRODUCE A DRYING DOWNSLOPE AREA ACROSS THE WESTERN HALF OF THE
CWA. THIS WILL PRODUCE A SHARP BOUNDARY BETWEEN RAINFALL TOTALS OF
ZERO... TENTH OF AN INCH... AND INCH OF QPF THROUGH TUESDAY. ALL
OF THE MODELS AGREE THAT THAT THE HIGHEST PRECIPITATION WILL FAST
NEAR THE MONTANA-NORTH DAKOTA BORDER.

TUESDAY NIGHT THROUGH WEDNESDAY... BRITISH COLUMBIAN TROUGH WILL
SWING THROUGH THE AREA AND PUSHING THE MESO-RIDGE OUT. A SECOND WAVE
OF PRECIPITATION IS EXPECTED BUT SHOULD BE LIGHTER WITH MOST OF
THE STABILITY COOLING ALREADY HAVING TAKEN PLACE FROM THE FIRST
WAVE OF SHOWERS. GAH/AEC


.LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY...
AFTERNOON UPDATE TO THE EXTENDED FORECAST: ONLY UPDATE WAS TO
INCREASE TEMPS A BIT SATURDAY AFTERNOON INTO MONDAY MORNING. THE
CURRENT FORECAST WAS AT THE BOTTOM END OF THE MODEL SPECTRUM
BLENDS AND SOME OF THE NEW MODELS SUGGEST IT COULD BE A TAD BIT
WARMER A A THERMAL RIDGE FROM DOWNSLOPING WINDS AND WAA PUSHES
INTO CENTRAL AND EASTERN MONTANA. FRANSEN

UPPER TROF OVER THE NORTHERN PLAINS EARLY IN THE PERIOD WILL MOVE
EAST TO THE GREAT LAKES WHILE A FLAT RIDGE BUILDS INTO THE
NORTHERN ROCKIES BY THE WEEKEND. GENERALLY DRY WEATHER EXPECTED
ALTHOUGH WITH VARIOUS SHORTWAVES DROPPING THROUGH THE NORTHWEST
FLOW THE OCCASIONAL SHOWER IS NOT OUT OF THE QUESTION. CURRENT
MODEL SOLUTIONS NOT INDICATING ENOUGH PROBABILITY TO GO ABOVE CLIMO
AT THIS TIME.

COLD FRONT DROPS INTO NORTHERN MONTANA ON THURSDAY BEHIND THE
EXITING UPPER TROF. THIS WILL BRING WINDY CONDITIONS WITH COLD AIR
ADVECTION DURING THE DAY...AND THE POTENTIAL FOR FREEZE OR FROST
BY FRIDAY MORNING WITH HIGH PRESSURE SLIDING INTO THE NORTHERN
PLAINS. TEMPERATURES THEN RECOVER TO NEAR OR A LITTLE ABOVE NORMAL
BY SATURDAY AS THE RIDGE BUILDS EAST. HOW LONG THE WARMER
TEMPERATURE REMAIN IS ALSO UNCERTAIN WITH THE POTENTIAL FOR
SHORTWAVE SUPPRESSING THE RIDGE AS THEY DROP OUT OF CANADA. EBERT


&&

.AVIATION...

MVFR TO IFR DUE TO LOWERED CEILINGS. LOW CLOUDS AND RAIN WILL
PREDOMINATE AT KSDY AND KGDV THROUGHOUT THE FORECAST PERIOD. KOLF
WILL REMAIN AT THE WESTERN EDGE OF THIS SYSTEM WITH LOW CLOUDS BUT
EXPECT SHOWERS TO BEGIN DIMINISHING AFTER 12Z. FURTHER WEST...
LOW CEILINGS AT KGGW WILL IMPROVE IN THE NEXT 12 HOURS. BRITTON


&&

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


&&

$$

WEATHER.GOV/GLASGOW




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