000
FXUS65 KGGW 121623 AAA
AFDGGW

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GLASGOW MT
923 AM MST FRI MAR 12 2010

.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH SUNDAY...
THE CHINOOK ARCHING THAT INHIBITED FOG PRODUCTION LAST NIGHT IS
STILL IN PLACE AS BROKEN HIGH STRATUS WHICH WILL ALLOW PLENTY OF
SUN THROUGH TO PRODUCE A MILD DAY. A SURFACE HIGH TO OUR SOUTHEAST
WILL SET UP A WEAK GRADIENT TO GENERATE A SOUTHEASTERLY BREEZE
TODAY...BUT NO STRONG WIND. THE DAY BEGAN WITHOUT MOST OF THE
USUAL FOG IN PLACE SO TEMPERATURES SHOULD APPROACH NORMAL IN MOST
AREAS. THE INHERITED GRIDS HANDLE EXPECTED CONDITIONS WELL...SO
FEW CHANGES NEEDED. SCT

PREVIOUS DISCUSSION...
UPPER RIDGE PUSHING INTO MONTANA WITH GOOD UPPER LEVEL MOISTURE
STREAM OUT OF THE EAST PACIFIC RESULTING IN CHINOOK ARCH CLOUDS
OVER CENTRAL MONTANA. BELOW THESE CLOUDS AIRMASS VERY DRY...
INCLUDING NEAR THE SURFACE AND THUS LITTLE FOG HAS DEVELOPED THIS
MORNING. RIDGING WILL SPREAD MUCH WARMER AIR INTO THE REGION TODAY
AND WITH SNOW OVER THE NORTHEAST...WILL REDEVELOP THE STRONG BUT
SHALLOW INVERSION. SHOULD BE ENOUGH SUNSHINE TODAY...EVEN THROUGH
THE HIGH CLOUDS FOR SNOW MELT TO ADD MOISTURE TO THE BOUNDARY
LAYER AND INCREASE THE POTENTIAL FOR MAINLY VALLEY FOG LATE
TONIGHT INTO SATURDAY MORNING.

UPPER TROF APPROACHING THE WEST COAST WILL HELP ENHANCE THE LEE
TROF/THERMAL BOUNDARY OVER CENTRAL MONTANA. THIS IN TURN WILL
STRENGTH THE EAST TO SOUTHEAST WINDS INTO NORTHEAST MONTANA...OFF
THE SNOW FIELDS OF NORTH DAKOTA...REENFORCING THE INVERSION AND
KEEPING TEMPERATURES BELOW GUIDANCE FOR MUCH OF THE REGION TODAY
AND TONIGHT.

PACIFIC UPPER TROF MOVES ACROSS THE ROCKIES ON SATURDAY...BUT LIKE
THE MAJORITY OF THE SYSTEMS IN THE PAST MONTH WILL BE SPLITTING
WITH MOST OF THE ENERGY PASSING AROUND EASTERN MONTANA. MOST OF
THE MOISTURE WILL BE WITH THE SOUTHERN PORTION OF THE WAVE...
KEEPING CHANCES OF PRECIPITATION VERY SMALL WITH THE SYSTEM.
HOWEVER ENOUGH ENERGY AND COLD AIR MAY BE AVAILABLE WITH THE
NORTHERN WAVE TO MIX OUT THE INVERSION OR WEAKEN IT TO KEEP FOG
FORMATION MINIMAL ON SATURDAY NIGHT INTO SUNDAY. EBERT

.LONG TERM...SUNDAY NIGHT THROUGH FRIDAY...
SUNDAY NIGHT THROUGH TUESDAY NIGHT... A TROUGH IS ANTICIPATED TO
EXIT THE REGION TO THE SOUTHEAST SUNDAY NIGHT ALONG WITH ANY
CHANCE FOR RAIN AND SNOW SHOWERS. A RIDGE WILL THEN QUICKLY TAKE
THE TROUGHS PLACE AND ACROSS NEMONT AND ALLOW FOR A RAPID WARM UP.
850 TEMPERATURES ARE EXPECTED TO RISE FROM NEAR 0*C TO A RANGE
7*C TO 12*C WHICH WILL ALLOW SURFACE TEMPERATURES TO RISE
THROUGHOUT THE REGION. IN ADDITION THE MOISTURE SOURCE FOR FOG
APPEARS TO BE WANING AS SNOW PACK ACROSS THE REGION HAS BROKEN
WITH PATCHES OF BARE GROUND NOW VISIBLE. MIXING IN THE ATMOSPHERE
HAS ALSO INCREASED WHERE ALL DAY INVERSIONS FOR THE BOUNDARY LAYER
ARE GETTING HARDER TO HOLD ON TO. THIS IS EVIDENT ESPECIALLY IN
THE HOURLY OBSERVATIONS WITH DAYTIME MINIMUM HUMIDITIES NO LONGER
REGULARLY EXCEEDING 80 PERCENT WHICH POINTS TOWARD WEAKER IF NOT
MORE NON- FOG EVENTS. OTHER THAN THIS EXPECT DRY CONDITIONS AND
PARTLY CLOUDY TO MOST CLEAR SKIES.

WEDNESDAY ONWARD... A SERIES OF THREE COLD FRONTS... WEDNESDAY...
THURSDAY... NEAR FRIDAY ARE ANTICIPATED IN A LARGE SCALE TROUGH
PATTERN. NORTHWEST FLOW BEHIND EACH FRONT WILL DROP SURFACE
TEMPERATURES AND UPPER LEVEL TEMPERATURES BACK TO BELOW AVERAGE.
THE THURSDAY COLD FRONT BARES THE MOST CHANCE FOR SNOW SHOWERS
WITH PACIFIC MOISTURE LOOKING TO ENTER DIRECTLY AHEAD OF IT. THE
TIMING OF THE THIRD AND FINAL COLD FRONT IS IN QUESTION HOWEVER
BOTH THE GFS AND EC APPEAR TO SHOW IT TO HAVE THE LARGEST
TEMPERATURE DIFFERENCE WITH 850 MB TEMPS DROPPED FROM NEAR ZERO
INTO THE NEGATIVE DOUBLE DIGITS. GAH

&&

.AVIATION...
A BEAUTIFUL FLYING DAY IS IN STORE FOR TODAY WITH SCATTERED TO
BROKEN UPPER LEVEL CLOUDS AROUND 20 KFT AND ABOVE. WINDS WILL HAVE
A SOUTHERLY COMPONENT AND BE LIGHT...UNDER 10 KTS...WELL INTO
THE EVENING. GIVEN THE SNOWMELT EXPECTED TODAY...FOG LOOKS LIKE A
GOOD POSSIBILITY LATE THIS EVENING AND OVERNIGHT TONIGHT.
GAH/GILCHRIST

&&

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

&&

$$

WEATHER.GOV/GLASGOW

NWS GGW Office Area Forecast Discussion