FXUS65 KMSO 241043
AFDMSO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
343 AM MST THU DEC 24 2009

.DISCUSSION...A NORTHERLY FLOW ALOFT WILL CONTINUE TO USHER DRIER
AND COLDER AIR INTO WESTERN MONTANA AND NORTH CENTRAL IDAHO TODAY.
THIS WILL LEAD TO A GENERALLY SUNNY DAY...WITH THE EXCEPTION OF
SOME LOW STRATUS EXPECTED TO DEVELOP OVER FLATHEAD LAKE AND OVER
PORTIONS OF THE IDAHO PANHANDLE. A RIDGE OF HIGH PRESSURE WILL
GRADUALLY SHIFT EASTWARD AND BEGIN TO INFLUENCE THE REGION TONIGHT
INTO THE WEEKEND...PROMOTING THE DEVELOPMENT OF VALLEY FOG AND
INVERSIONS BY SATURDAY MORNING. IN ADDITION...GENERALLY CLEAR
SKIES AND LIGHT WINDS WILL ENCOURAGE STRONG RADIATIONAL COOLING.
THIS WILL MAKE FOR VERY COLD MORNINGS WITH TEMPERATURES SLOW TO
WARM THROUGH THE DAY.

SUNDAY THROUGH THURSDAY... A LOW PRESSURE TOUGH OFF THE WEST COAST
WILL SPLIT WITH TWO UPPER LEVEL JET STREAMS DEVELOPING.
ONE JET WILL BE WELL TO THE NORTH THROUGH CANADA AND THE OTHER
IN THE FAR SOUTHERN EXTENT OF THE COUNTRY. THIS PATTERN WILL
KEEP THE NORTHERN ROCKIES UNDER A BENIGN WEATHER PATTERN INTO
THE BEGINNING OF THE WEEK. THE WEATHER PATTERN DOES APPEAR TO
BECOME MORE ACTIVE WITH WEAK SHORTWAVES OF ENERGY MOVING INTO THE
PACIFIC NORTHWEST BY THE LATTER HALF OF THE EXTENDED FORECAST PERIOD.
CHANCES FOR PRECIPITATION WILL INCREASE AROUND TUESDAY AS BOTH THE
GFS AND ECMWF PERSISTENTLY SHOW A NORTHWESTERLY FLOW WITH A SHORTWAVE
TROUGH PASSAGE THROUGH THE REGION.
&&

.AVIATION...A DRY NORTHERLY FLOW ALOFT WILL PROMOTE GENERALLY
PLEASANT FLYING CONDITIONS OVER THE NORTHERN ROCKIES TODAY. A FEW
AREAS OF LOW STRATUS AND FOG HAVE DEVELOPED THIS MORNING AND ARE EXPECTED
TO PERSIST OVER THE IDAHO PANHANDLE AND ACROSS NORTHWEST MONTANA.
IN THESE AREAS...LOW CEILINGS MAY CAUSE THE HIGHER TERRAIN TO BE
OBSCURED. OTHERWISE...LIGHT WINDS AND GENERALLY CLEAR SKIES WILL PREVAIL.

&&

.AIR STAGNATION...CLEARING SKIES AND CALM WINDS AT THE SURFACE WILL
PROMOTE STRENGTHENING INVERSIONS THROUGH THE WEEKEND. A RIDGE OF HIGH
PRESSURE WILL APPROACH THE INTER- MOUNTAIN REGION FROM THE WEST
FURTHER STABILIZING THE LOWER ATMOSPHERE THROUGH THE WEEKEND. 

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
ID...NONE.
&&

$$

SHORT TERM...PALLISTER
LONG TERM....KITSMILLER
AVIATION...PALLISTER