[MCD] SWOMCD

[MCD at goshenarc.org]

ACUS11 KWNS 182029
SWOMCD
SPC MCD 182028 
CAZ000-182230-

MESOSCALE DISCUSSION 0167
NWS STORM PREDICTION CENTER NORMAN OK
0228 PM CST FRI FEB 18 2005

AREAS AFFECTED...CNTRL/SRN CALIFORNIA COASTAL RANGES...SAN JOAQUIN
VALLEY

CONCERNING...CONVECTIVE TRENDS 

VALID 182028Z - 182230Z

THUNDERSTORMS ARE EXPECTED TO DEVELOP/INCREASE WITHIN THE NEXT
COUPLE OF HOURS...PARTICULARLY NEAR/EAST OF THE COASTAL RANGES...
SOUTH/SOUTHWEST OF SAN FRANCISCO/SACRAMENTO/FRESNO.  SOME MAY
PRODUCE HAIL/GUSTY WINDS.

OBJECTIVE GUIDANCE INDICATES WEAK DESTABILIZATION IS ONGOING ALONG
THE CALIFORNIA COASTAL RANGES...FROM THE SANTA MARIA AREA NORTHWARD
TO THE VICINITY OF SAN FRANCISCO BAY.  THIS IS MAINLY DUE TO SURFACE
HEATING OF MOIST BOUNDARY LAYER...WITH LOWER/MID 50S DEW POINTS...
BENEATH EASTERN PERIPHERY OF MID-LEVEL COLD POOL ASSOCIATED WITH
OFFSHORE UPPER LOW.

MID-LEVEL SUBSIDENCE IN WAKE OF WEAK IMPULSE EMBEDDED WITHIN
CYCLONIC UPPER FLOW REGIME CURRENTLY APPEARS TO BE INHIBITING DEEPER
CONVECTIVE DEVELOPMENT.  HOWEVER...SHORT WAVE TROUGH CONTINUES TO
LIFT NORTH/EAST OF THE SAN FRANCISCO BAY/SAN JOAQUIN VALLEY AREA...
AND INHIBITION IS EXPECTED TO WEAKEN SUFFICIENTLY FOR THUNDERSTORM
ACTIVITY BY THE 22-23Z TIME FRAME.  EASTERLY UPSLOPE COMPONENT IN
THE LEE OF THE COASTAL RANGES WILL AID FORCING FOR DEVELOPMENT...AND
WILL SOMEWHAT ENHANCE VERTICAL SHEAR BENEATH WEAK TO MODERATE
SOUTHWESTERLY MID/UPPER FLOW.

MOST UNSTABLE CAPE IN EXCESS OF 500 J/KG APPEARS LIKELY BY LATE
AFTERNOON...AND MODEL FORECAST SOUNDINGS SUGGEST FAVORABLE
THERMODYNAMIC STRUCTURE FOR HAIL IN STRONGER CELLS...ONE OR TWO OF
WHICH MAY BRIEFLY APPROACH OR EXCEED SEVERE LIMITS.

..KERR.. 02/18/2005

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

ATTN...WFO...HNX...LOX...STO...MTR...

37712220 38182157 37892085 37242001 36751981 36341977
35701984 35412022 35752069 36382155 

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