FXUS65 KGGW 270933
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
233 AM MST FRI NOV 27 2009
.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH SUNDAY...
TODAY THROUGH TONIGHT... SYNOPTICLY A RIDGE IS ANTICIPATED TO
LEAVE THE CWA THROUGH THE MORNING HOURS AS A LONG WAVE TROUGH
STRETCHED OUT FROM SOUTHERN ALBERTA TO CENTRAL CALIFORNIA MOVES
INTO THE AREA. THIS SHOULD LEAD TO DRY CONDITIONS THROUGH MOST OF
THE DAY WITH A FEW ISOLATED RAIN SHOWERS POKING THERE HEADS IN BY
THE EVENING HOURS. DUE TO A SHORTWAVE AND FRONTAL PASSAGE
TEMPERATURES ARE ANTICIPATED TO DROP THROUGHOUT THE NIGHT TIME
HOURS WITH ANY RAIN SHOWERS TRANSITIONING TO SNOW SHOWERS.
PRECIPITATION CHANCES SEEMED TO HAVE STRENGTHENED SOMEWHAT FROM
LAST NIGHT AS MODEL FORECAST SOUNDINGS HAVE DRAMATICALLY LOWERED THE
THE LAYER OF MOISTURE ON WHICH WET BULB EFFECTS INITIALLY TAKE
PLACE... FROM 700 MB TO 850 MB. THIS SIGNIFICANTLY REDUCES THE DEPTH
OF DRY AIR... ROUGHLY 4000 FT... THAT MUST BE MOISTENED BEFORE
PRECIPITATION REACHES THE GROUND. EVEN STILL... WITH 850 TEMPERATURES
STRADDLING THE 0*C LINE AND 1000-500 MB THICKNESSES AT OR NEAR THE
540 DM LINE SNOW RATIOS WILL BE VERY LOW GENERATING ONLY AND INCH
OR LESS OF EQUIVALENT ACCUMULATION. EVEN IF SNOW TOTALS WERE HIGH...
SURFACE TEMPERATURES ARE CURRENTLY IN THE MID TO UPPER 30S ACROSS
THE REGION WITH SUB-SURFACE TEMPERATURES IN THE LOWER 40S WHICH
SHOULD RAPIDLY MELT ANY SNOW REACHING THE GROUND. TRENDS IN SPEEDS
OF MODEL WIND FIELDS ALSO CONTINUE TO DIMINISH POINTING MORE
TOWARDS A NON-EVENT AT THIS TIME.
SATURDAY THROUGH SUNDAY... A DRY SLOT IN NORTHWEST FLOW IS
ANTICIPATED TO MOVE INTO THE REGION QUICKLY BEHIND THE SYSTEM
ENDING CHANCES OF PRECIPITATION TO ALL BUT THE SOUTH EASTERN
PORTIONS OF THE CWA BY SATURDAY AROUND NOON. SATURDAY NIGHT AND
SUNDAY SHOULD ALSO BE DRY WITH PARTLY CLOUDY TO CLEAR CONDITIONS
EARLY ON. BY SUNDAY AFTERNOON CHINOOK ARCHING MAY HAVE A CHANCE TO
BRING MORE CLOUDY SKIES ON WITH A SLIGHT REBOUND IN SURFACE
TEMPERATURES. GAH
.LONG TERM...SUNDAY NIGHT THROUGH FRIDAY...
THE EXTENDED FORECAST PERIOD BEGINS ON MONDAY WITH A RIDGE OVER
THE WEST COAST ROLLING OVER A UPPER LOW IN THE BAJA REGION.
SOMEWHAT OF A SPLIT FLOW PATTERN STILL EXISTS. WESTERLY FLOW UNDER
THE RIDGE ON MONDAY WILL PROVIDE MAX TEMPS SLIGHTLY ABOVE NORMAL. THE
RIDGE BREAKS DOWN AS A TROUGH MOVES IN FROM CANADA IN NORTHWEST
FLOW.
THE FRONT MOVES IN ON TUESDAY AFTERNOON. AT THIS POINT THE GFS
SEEMS TO HAVE THE BETTER HANDLE ON IT AND HAS BEEN MORE
CONSISTENT. IN PAST RUNS THE EC HAS TRIED TO MATCH UP WITH THE GFS
MORE. THE GFS IS DRIER THAN THE EC AND TRACKS THE LOW MORE EAST
RATHER THAN SE SPARING OUR FORECAST AREA THE BRUNT OF THE ARCTIC
AIRMASS. THE BEST CHANCE FOR PRECIP IS TUESDAY AFTERNOON FOR THE
CWA BUT EVEN AT BEST IS A SLIGHT CHANCE POPS FOR THE AREA. NOT
MUCH IN THE WAY OF MEASURABLE PRECIP IS EXPECTED AT THIS POINT. THE
ARCTIC AIRMASS WILL PUSH THROUGH TUESDAY EVENING AND BRING MAX
TEMPS FOR WED AND THU BACK TO NORMALS. THE PASSAGE OF THE FRONT
TUESDAY EVENING WILL BRING A CONCERN FOR STRONG NW WINDS TUE NIGHT
AND WED.
AFTER WED THE CONSISTENCY IN THE MODELS DROP AS THE GFS WANTS TO
DROP A CLOSED LOW DOWN THE EAST COAST AND KEEP THE FORECAST AREA
ON THE OUTER EDGE OF THE ARCTIC AIR. THE EC WANTS TO BRING A RIDGE
ASHORE AND WARM THE AREA UP. THE ENSEMBLES ALSO SHOW MUCH
UNCERTAINTY. FELT THE BEST CONFIDENCE IS TO STAY CLOSE TO
CLIMATOLOGY FOR FRI AND INTO NEXT WEEKEND. SHALLENBERGER
&&
.AVIATION...
VFR CONDITIONS EXPECTED TODAY WITH MID TO HIGH CLOUDS OVER THE
REGION. A WEAK BOUNDARY WILL DROP OUT OF CANADA THIS MORNING...
TURNING WINDS NORTHWEST. AN UPPER WAVE WILL CROSS THE REGION
TONIGHT BRINGING A POSSIBILITY OF A RAIN OR SNOW SHOWER. RAE
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
WEATHER.GOV/GLASGOW
