RAH Discussion

[Suncat]

From RAH NWS...

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
250 PM EST THU JAN 29 2004

.DISCUSSION...

TONIGHT THROUGH SAT: STABLE AIR NEAR/ABOVE MOUNTAIN TOP LEVEL AND
ACCELERATING WNW FLOW WITH HEIGHT WILL CONTINUE TO MAKE CONDITIONS
SOMEWHAT FAVORABLE FOR OROGRAPHICALLY ENHANCED HIGH CLOUDS. SHEARED
UPPER VORT MAX ARRIVES FOR TONIGHT & EXPECT PARTLY TO MOSTLY CLOUDY
SKIES. SURFACE FROPA FROM THE NW FRI SHOULD BE DRY WITH WESTERLY LOW
LEVEL FLOW AHEAD OF IT. LOWS 29-33 TONIGHT & HIGHS 44-52 FRI... A
BIT BELOW GUIDANCE AND ABOVE THOSE INDICATED BY PROGGED THICKNESSES
CONSIDERING TODAY'S WARMER TEMPS & THE POTENTIAL FOR THE COOLER AIR
TO BE RETARDED BY THE MOUNTAINS. COOL SURFACE HIGH BUILDS IN FROM
THE WNW FRI NIGHT/SAT WITH RISING HEIGHTS ALOFT AS SOUTHWEST
SHORTWAVE TROUGH MOVES INTO THE WEST GULF & DEEPENS. CHILLY 20S FRI
NIGHT THEN COOLER HIGHS FOR SAT OF ABOUT 39-47.

SUN-TUE: SURFACE HIGH MOVES INTO A DAMMING POSITION CENTERED OVER
THE NORTHWEST US ON SUNDAY. SHORTWAVE AND ITS PRECIP IS PROGGED TO
HOLD TO OUR SOUTH THROUGH SUN/SUN NIGHT & WILL KEEP THIS PERIOD DRY
BUT WITH INCREASING CLOUDS. FORECAST BECOMES DIFFICULT SINCE THIS
PARENT HIGH MAY TAP INTO THE VERY COLD AIR SOURCE (-15 TO -25
DEGREES CURRENTLY) OVER THE NORTHERN PLAINS/SCENTRAL CANADA... OR IT
MAY BE A MORE MILD TX-SOURCE HIGH... AND THIS WILL DIRECTLY AFFECT
THE DEPTH OF LOW LEVEL COLD AIR & THE RESULTANT PTYPE. IT APPEARS
THAT UNLIKE THIS LATEST CLASSICAL DAMMING EVENT...IN WHICH THE HIGH
WAS ANCHORED ALOFT BY STRONGLY CONFLUENT FLOW TO HELP PROVIDE A
CONSTANT COLD AIR SOURCE... THIS UPCOMING HIGH WILL NEED TO BE
ANCHORED BY RIDGING ALOFT. AS THE WHOLE PATTERN IS FAIRLY
PROGRESSIVE... THE HIGH SHOULD BE TRANSIENT CULMINATING IN MORE OF
AN IN SITU DAMMING EVENT. WILL GO WORST CASE SCENARIO (OF TAPPING
INTO THE VERY COLD CANADIAN AIR) SINCE WE'RE SO CLOSE ON THE HEELS
OF THIS RECENT WINTERY WEATHER EVENT... AND WILL FOLLOW PTYPES
INDICATED BY GFS THICKNESSES MINUS 10-20M IN THE LOW LEVELS. THIS
SUPPORTS AN INITIAL PTYPE EARLY (MON MORNING) OF FREEZING RAIN MIXED
WITH A LITTLE SLEET IN THE NORTHWEST PIEDMONT... BUFFERED BY A STRIP
OF RAIN OR FREEZING RAIN OVER THE REST OF THE PIEDMONT. THICKNESSES
WARM UP TO ALL RAIN MON AFTERNOON BUT WILL DELAY THE TRANSITION BY A
FEW HOURS. AFTER COLLABORATION WITH NEIGHBORING OFFICES... WILL
TRANSITION TO A COLD RAIN MON NIGHT... WHEN WILL HAVE HIGHEST POPS
(50%) AS THE LEFT FRONT QUAD OF THE SOUTHERN STREAM JET APPROACHES
ALONG WITH PVA. THIS ALL SHOULD CLEAR THE CWA TUE BUT WILL CARRY A
SMALL CHANCE POP IN THE MORNING.

WED-THU: GFS SHOWS YET ANOTHER SRN STREAM UPPER LOW ZIPPING ACROSS
NRN MEXICO INTO THE SRN PLAINS... BUILDING RIDGING UPSTREAM... BUT
SURFACE HIGH THAT BUILDS IN IS RATHER COOL. WILL KEEP WED-THU DRY
WITH TEMPS A FEW DEGREES BELOW NORMAL.

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Seems as 'tho they are not seeing a major winter event for central NC for next week!