[MCD] SWOMCD

Mon Dec 19 01:00:29 UTC 2005

ACUS11 KWNS 190058
SWOMCD
SPC MCD 190057 
UTZ000-IDZ000-NVZ000-ORZ000-WAZ000-190600-

MESOSCALE DISCUSSION 2581
NWS STORM PREDICTION CENTER NORMAN OK
0657 PM CST SUN DEC 18 2005

AREAS AFFECTED...SW WA/MUCH OF ORE/SW ID/NRN UT

CONCERNING...FREEZING RAIN/SNOW 

VALID 190057Z - 190600Z

...FZRA WILL AFFECT THE INTERIOR VALLEYS OF NW ORE/SW WA TONIGHT
WITH MODERATE/HEAVY SNOW FROM THE COLUMBIA GORGE SEWD TO SW ID/NRN
UT...

FIRST IN A SERIES OF UPPER IMPULSES IS NOW ROTATING ONSHORE WITH AN
UPPER CIRCULATION CENTER APPARENT IN EVENING WATER VAPOR IMAGERY
MOVING INTO SW ORE. STAGNANT COLD AIRMASS HAS BEEN TRAPPED WITHIN
THE VALLEYS FOR THE PAST FEW DAYS...AND WITH STRONG LARGE SCALE
ASCENT AND MOISTURE IN PLACE...FZRA WILL RESULT ACROSS SOME
LOCATIONS TONIGHT. THERE HAS BEEN FZRA DURING THE LAST COUPLE OF
HOURS AT SALEM AND IN EUGENE EARLIER. 00Z SOUNDING FROM SALEM SHOWED
NEAR FREEZING TEMPS FROM ABOUT 925MB-750MB...BUT RECENT MODERATE
SNOW REPORTS IN/NEAR PORTLAND INDICATE THE COLUMN IS COLD ENOUGH FOR
SNOW AT LEAST INITIALLY. VEERING PROFILE FROM BOTH ORE UPPER AIR
SOUNDINGS IMPLIES CONTINUED WARMING...WITH A MIX OF PCPN TYPES
POSSIBLE.

FORECAST SOUNDINGS FROM THE NAM/RUC SUGGEST FZRA COULD SPREAD FROM
PORTLAND NWD INTO THE INTERIOR VALLEYS OF SW WA BY 03Z AND NEAR
OLYMPIA TOWARD 06Z. THE PTYPE ALGORITHM AND THE NCEP SREF SHOW AN
EVEN STRONGER SIGNAL OF FZRA...ESPECIALLY AFTER 06Z. ACROSS NERN
PORTIONS OF ORE INTO ID/UT...SNOW IS EXPECTED WITH HRLY RATES OF 1
TO 2 INCHES PER HOUR POSSIBLE...AND BOUTS OF HEAVY SNOW WILL ALSO
CONTINUE OVERNIGHT ACROSS THE WASATCH.

..TAYLOR.. 12/19/2005

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...SLC...PIH...BOI...LKN...OTX...PDT...SEW...PQR...

41311512 44102090 44762407 46692299 47432121 45381690
41701120 40691196 

WWWW