Based on the EWX AFD this morning, there is a hint that the air mass may be more moist at the surface this go around down here, reducing any wet-bulb cooling, thereby reducing whatever frozen chances we have. Then there is a question about the amount of QPF available, maybe getting drizzle at best. Then the latest lone wolf model shows a healthy QPF where it didn't before. Silly computers.
Who knows? I'm tired of Winter teases.
Bring on split flow, Spring rains, and regular MCSs.
.PREV DISCUSSION... /ISSUED 422 AM CST FRI FEB 20 2015/
OUR NEXT BIG COLD FRONT PASSAGE WILL OCCUR LATE SATURDAY...WITH
THE WIND SHIFT PROGGED TO BEGIN ENTERING THE NORTHERN ZONES BY
AROUND 00Z SUNDAY.
LONG TERM (SATURDAY NIGHT THROUGH THURSDAY)...
THE COLD FRONT SHOULD COOL HIGHS INTO THE 50S FOR THE NORTHERN
HALF OF THE CWA.
850 MB FLOW QUICKLY RECOVERS TO A SOUTHERLY
DIRECTION AND AN OVERRUNNING PATTERN SETS UP ACROSS THE SOUTHERN
HALF OF THE STATE. THIS WILL EFFECTIVELY MOISTEN THE LOW LEVEL
ATMOSPHERE AS CAA BECOMES STRONGEST SUNDAY NIGHT AND INTO MONDAY
MORNING. THE QUESTION...AS IS TYPICALLY THE CASE...IS HOW COLD
WILL THE TEMPERATURES DROP TO AND HOW FAR SOUTH. SIMILAR EVENTS
SUCH AS THIS...WITH STRONG SFC CAA AND COMPETING SOUTHERLY 850 MB
FLOW AND OVERRUNNING HAS MADE IT DIFFICULT FOR SFC TEMPERATURES TO
DROP TO WHAT GUIDANCE HAS ADVERTISED. FORECAST SOUNDINGS ARE
PLENTY MOIST IN THE LOW LEVELS SO THE POTENTIAL FOR WET BULBING
APPEARS TO BE SLIM...SO THE CAA WILL BE COMPETING WITH CLOUDY
SKIES...A MOIST COLUMN BEING FED BY SOUTHERLY 850 FLOW...AND
GROUND TEMPERATURES THAT SHOULD BE PRETTY WARM. GFS FORECAST
SOUNDINGS AS WELL AS ECMWF LOOK LIKE MOSTLY A COLD RAIN BUT NAM
SOUNDINGS WERE QUITE A BIT COLDER JUST OFF THE SURFACE. SO DID NOT
FEEL CONFIDENT IN REMOVING THE WINTRY PRECIP THAT THE PREVIOUS
FORECAST INCLUDED.
STILL THINK QPF VALUES WILL BE LOW AND
ACCUMULATION POTENTIAL WILL BE LIGHT AT BEST THROUGH MID MORNING
MONDAY.A COLD WET DAY WILL PERSIST MONDAY AS THIS OVERRUNNING PATTERN
CONTINUES. TUESDAY NIGHT DOES APPEAR TO BE A BIT COLDER ACROSS THE
NORTH AND WITH MODELS SHOWING SLIGHT CHANCE POPS LINGERING...HAD
TO INCLUDE WINTRY PRECIP...IN THE FORM OF FREEZING RAIN...ON THE
ESCARPMENT AND SOUTHERN HILL COUNTRY TUESDAY MORNING AS WELL.
THE
QUESTION HERE ISNT SO MUCH THE TEMPERATURES BUT WHETHER OR NOT WE
GET ANY QPF. THE BEST MOISTURE APPEARS TO BE EXITING THE AREA SO
THIS MAY JUST BE IN THE FORM OF DRIZZLE IF ANYTHING. STILL NOT
EXPECTING MUCH IF ANY ACCUMULATIONS BUT BEING THE SECOND DAY OF
COLD TEMPERATURES...SOME SPOTS MAY BECOME SLICK OF QPF DOES
DEVELOP.
ITS AT THIS POINT THAT SUBSTANTIAL MODEL DIVERGENCE BEGINS IN THE
GFS AND EURO. IN GENERAL...A CLOSED LOW HOVERING OVER THE SAN
FRANCISCO BAY AREA WILL PHASE WITH CANADIAN TROUGHING AND BEGIN TO
TRAVERSE THE ROCKIES.
THIS AREA OF LOW PRESSURE COINCIDES WITH THE
CANADIAN TROUGH AXIS BY WEDNESDAY MORNING IN THE GFS AND IF
SO...WOULD PRODUCE SOME HEALTHY QPF. THIS IS STARKLY DIFFERENT
FROM THE ECMWF SOLUTION HOWEVER AND A NEW DEVELOPMENT FROM
PREVIOUS RUNS. THEREFORE LEFT SUPERBLEND SOLUTION AS IS AND ONLY
ADJUSTED TO MESH WITH NEIGHBORS FOR NOW.
&&
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