Heavy Snow in Washington, March 15 to 17, 2002

EASTERN WASHINGTON AND NORTH IDAHO AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WASHINGTON
230 PM PST FRI MAR 15 2002

AN UNSEASONABLY COLD AND SHOWERY WEATHER PATTERN WILL CONTINUE OVER
THE INLAND NW THIS WEEKEND AND INTO NEXT WEEK. AN UPPER LOW WILL
SETTLE OVER WA SATURDAY AND SUNDAY...BRINGING SNOW TO THE NORTHERN
MOUNTAINS. THIS LOW WILL DRIFT TO THE SOUTHEAST BY MONDAY...BUT A
SECOND UPPER LOW WILL DEVELOP OVER WA BY MID WEEK.

.IN THE SHORT TERM...RADAR IS STARTING TO LIGHT UP WITH MORE
AFTERNOON SHOWER ACTIVITY. THE SENSIBLE WEATHER MAY SEEM NO DIFFERENT
THAN THE PAST SEVERAL DAYS...BUT THE ELEMENTS LEADING TO THE SHOWERS
ARE. INSTEAD OF A VERY UNSTABLE AIRMASS WITH DIURNAL DRIVEN
CONVECTION...WEAK DYNAMICS AND WAA WITH A MODERATELY UNSTABLE AIRMASS
HAS LEAD TO THE WIDESPREAD SHOWERS. WILL SEE THESE SHOWERS TAPER OFF
THIS EVENING...BUT THE BREAK WILL BE BRIEF. AS THE UPPER LOW BEGINS
TO BE CARVED OUT OVER WRN WA...A SHORTWAVE WILL SWEEP ACROSS THE
CASCADES INTO N IDAHO LATE TONIGHT INTO SATURDAY. THE MESO ETA AND
MM5 SHOW A BAND OF LIGHT SNOW WITH THIS UPPER TROF TO SPREAD THROUGH
THE REGION...AND HANG UP OVER THE NRN ZONES. AT THE SAME TIME...A
SURFACE LOW WILL DEEPEN OVER SRN BC AND SLOW DRIFT TO THE WA/BC
BORDER BY SATURDAY. THIS WILL PROVIDE THE CONVERGENCE FOR SNOW TO
CONTINUE ALONG THE BORDER THROUGH THE DAY AS SNOW LEVELS WILL DROP TO
THE VALLEY FLOORS AND REMAIN THERE THROUGH THE DAY.

BY SATURDAY NIGHT INTO SUNDAY...THE SURFACE LOW WILL GRADUALLY WEAKEN
AND DRIFT SOUTHWARD. AS IT DOES...AN ARCTIC FRONT WILL SAG INTO NRN
ZONES. EXPECT A BAND OF HEAVY SNOW TO BREAK OUT ALONG THIS FRONT. THE
RETURN EASTERLY FLOW JUST BEHIND THIS FRONT HAS THE POTENTIAL FOR
HEAVY SNOWS IN THE EAST SLOPES. COLDER AND DRIER AIR WILL GRADUALLY
SETTLE INTO THE NRN ZONES...EVENTUALLY BRINGING AN END TO THE SNOW.
AGAIN THIS BREAK WILL BE SHORT LIVED....AS THE AVN INDICATES AN
OVERRUNNING PATTERN SPREADING ACROSS THE INLAND NW BY MONDAY
AFTERNOON. RFOX

IN THE EXTENDED...ONCE AGAIN BIG CHANGES IN THE PROGS BUT AT LEAST
NOW THEY ARE IN SOME AGREEMENT. LASTEST TREND IS TO DEVELOP AN EAST-
WEST TROUGH OVER SOUTHERN CANADA AND IN TIME DEVELOP A LOW WHICH WILL
DROP DOWN OVER WASHINGTON. THEN THE PROGS DIFFER WITH THE ECMWF
DROPPING THE LOW SOUTHWARD WHILE THE MRF MOVES THE LOW EASTWARD AS A
TROUGH. COLD AIR WILL LIE JUST NORTH OF THE BORDER AND ONE OF THE BIG
QUESTIONS WILL BE WHAT HAPPENS TO THIS COLD FRONT AND COLD AIR. THE
PROBLEM WILL BE IN HOW MUCH PRECIPITATION WILL FALL OVER NORTHERN
BORDER OF OUR CWA. IF THE COLD AIR MOVES FAR ENOUGH SOUTH THE
PRECIPITATION COULD BE SIGNIFICANT...IF IT STAYS TO THE NORTH THE
SIGNIFICANT PRECIPITATION WILL BE IN CANADA. SINCE THIS IS THE FIRST
SET OF PROGS WITH THIS BIG CHANCE WILL JUST GO WITH CHANCE POPS FOR
THE TUESDAY THROUGH THURSDAY PERIOD AND LET LATER SHIFTS DEAL WITH
ANY NEEDED ADJUSTMENTS.  WILL GO WITH A DRYING TREND ON FRIDAY AS NEW
PROGS SHOW A DRIER NORTHERLY FLOW.  LH

...THE INFORMATION IN THIS PRODUCT CONCERNING WARNINGS AND FORECASTS
IS VALID ONLY AT THE TIME OF ISSUANCE. THE LATEST WARNING AND
FORECAST INFORMATION WILL BE FOUND IN THE APPROPRIATE PRODUCTS...

GEG 028/037/022/033/016/034 786844
COE 029/035/021/032/013/033 787844
PUW 028/037/023/034/017/035 686654
LWS 031/040/026/037/024/038 675544
CQV 029/035/020/029/013/030 898534
SPT 028/036/018/027/011/029 898534
WWP 029/034/024/031/016/032 786733
EAT 030/043/027/038/024/039 454624
MWH 030/044/025/040/022/041 543624

.OTX...HEAVY SNOW WARNING LATE TONIGHT AND SATURDAY
        WAZ037 WAZ038 IDZ01
       WINTER WEATHER ADVISORY FOR SNOW SATURDAY IDZ04
       WINTER STORM WATCH SATURDAY NIGHT AND SUNDAY WAZ042