FXUS62 KRAH 110804
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
304 AM EST FRI DEC 11 2009
.SYNOPSIS...
COOL HIGH PRESSURE WILL BUILD INTO THE REGION TODAY... AND LINGER
THROUGH SATURDAY. A LOW PRESSURE SYSTEM WILL MOVE UP THE SOUTHEAST
COAST SATURDAY NIGHT AND SUNDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 300 AM...
WITH ONLY A LITTLE HIGH CLOUDINESS TO CONTEND WITH TODAY...
TEMPERATURES SHOULD APPROACH FULL SUN VALUES. WINDS IN THE MIXED
LAYER CONTINUE TO DECLINE AND LITTLE DOWNSLOPE WARMING NOR THE WIND
SPEEDS TO ADVECT SUCH WARMING EAST IS EXPECTED. WITH AFTERNOON LOW
LEVEL THICKNESSES BELOW 1300 METERS... HIGH TEMPERATURES OF 42
NORTHWEST TO 47 SOUTHEAST.
SURFACE HIGH PRESSURE SETTLES OVER NORTH CAROLINA TONIGHT AND THE
AIR MASS WILL BE QUITE DRY. CALM FOR MOST OF THE NIGHT AND URBAN AND
RURAL LOW SPOTS WILL LIKELY SHOW DECENT VARIATION IN TEMPERATURES.
WITH LITTLE CHANGE IN THICKNESS FROM THE AFTERNOON... LOW
TEMPERATURES SHOULD BE NEAR THE COLD SIDE OF CLIMATOLOGY FOR THE
EXPECTED THICKNESS... WITH MOST LOW TEMPERATURES RANGING FROM 22 TO
25.
&&
.SHORT TERM /SATURDAY THROUGH SUNDAY/...
AS OF 230 PM THURSDAY...
ISENTROPIC LIFT OVER THE SURFACE RIDGE IS EXPECTED TO INCREASE
DURING THIS TIME FRAME WHILE THE AIR COLUMN ALSO BEGINS TO SATURATE
FROM THE TOP DOWN. CENTRAL NORTH CAROLINA SHOULD STAY DRY DURING THE
DAY ON SATURDAY AS ANY PRECIP THAT FORMS WILL EVAPORATE AS IT
ENCOUNTERS THE DRY SURFACE AIR MASS. AS THE RIDGE SHIFTS OFF TO THE
EAST LATE SATURDAY INCREASED LOW LEVEL FLOW WILL ALLOW MOISTURE TO
FINALLY INCREASE AT THE SURFACE. RAINFALL IS EXPECTED TO INCREASE IN
COVERAGE AFTER 00Z SUNDAY FROM THE SOUTHWEST TO NORTHEAST WITH THE
INCREASED ISENTROPIC LIFT AND A DEVELOPING INVERTED TROUGH OFF THE
CAROLINA COAST. THERE WILL BE A VERY SMALL WINDOW FOR SOME TYPE OF
WINTRY MIX AT THE ONSET OF THE EVENT LATE SATURDAY NIGHT ACROSS THE
EXTREME NORTHWESTERN PORTION OF THE CWA. WARM ADVECTION AT MID
LEVELS WILL INCREASE H85-H7 THICKNESSES ABOVE 1550M....WHILE H10-H85
THICKNESSES ARE FORECAST TO BE AT OR JUST ABOVE 1300M FROM THE TRIAD
AND NORTHWARD. THIS THERMAL PROFILE WOULD SUPPORT A SMALL CHANCE OF
FREEZING RAIN OR DRIZZLE. LATEST HPC FORECAST IS ALSO INDICATING A
POSSIBLE TRACE EVENT OVER THIS REGION...BEFORE THE PRECIP QUICKLY
CHANGES OVER TO RAIN AS INDICATED BY THE PREDOMINATE P-TYPE
NOMOGRAM. MODELS HAVE BEEN TRENDING WARMER OVER THE PAST FEW RUNS
AND IF THIS CONTINUES...THIS WOULD LIKELY TURN INTO AN ALL RAIN
EVENT. NEVERTHELESS...THIS WILL BE CLOSELY MONITORED BY FUTURE
SHIFTS. OTHERWISE...WILL SHOW LIKELY POPS ACROSS THE REGION THROUGH
18Z ON SUNDAY BEFORE THINGS FINALLY BEGIN TO TAPER OFF AS THE
SURFACE LOW OFF THE COAST MOVES NORTHEAST. AM NOT EXPECTING TOO MUCH
IN THE WAY OF QPF (AROUND 1/3 OF AN INCH) FOR THE DURATION OF THIS
EVENT...AS FORECAST SOUNDINGS DO NOT FORECAST A DEEP LAYER OF MOISTURE
(ONLY SATURATED BELOW ABOUT 600MB). ALSO...ONLY WEAK UPPER LEVEL
SUPPORT WILL BE IN PLACE ACROSS THE REGION OVER THE WEEKEND. MAY SEE
TWO QPF MAXIMUMS...ONE ALONG EASTERN PORTIONS OF THE CWA DUE TO THE
PROXIMITY OF THE SURFACE LOW AND ANOTHER ACROSS THE PIEDMONT DUE TO
THE UPSLOPE EFFECT. WITH PRECIP AND AMPLE CLOUD COVER IN
PLACE...WILL CONTINUE TO FORECAST TEMPS ON THE COOL SIDE OF
GUIDANCE...WITH AFTERNOON HIGH TEMPERATURES MOSTLY IN THE MID TO
UPPER 40S.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 255 AM FRIDAY...
THE COASTAL LOW... DEEP CLOUD COVER... AND PRECIPITATION CHANCES
SHOULD PULL AWAY FROM THE MID ATLANTIC COAST SUNDAY NIGHT. THE
EXPECTED CLEARING SKIES AND LIGHT STEERING FLOW (ASSOCIATED WITH A
WEAK SURFACE RIDGE) MAY PROMOTE THE DEVELOPMENT OF PATCHY FOG OR LOW
STRATUS BY MONDAY MORNING. LOWS GENERALLY 35 TO 40 DEGREES.
MONDAY THROUGH THURSDAY: EXPECT A BRIEF WARM UP MONDAY AHEAD OF THE
NEXT TROUGH ALOFT... ATTENDANT SURFACE COLD FRONT... AND CHANCE OF
SHOWERS PROJECTED TO CROSS CENTRAL NC TUESDAY OR TUESDAY NIGHT. THE
MILDER TEMPERATURES IN THE UPPER 50S TO LOWER 60S MONDAY (AND
PERHAPS AGAIN TUESDAY PENDING THE FRONTAL PASSAGE TIMING) WILL
TURN COOLER BEHIND THE FRONT... WITH HIGHS IN THE MIDDLE 40S TO
LOWER 50S EXPECTED ON WEDNESDAY AND THURSDAY.
&&
.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
AS OF 110 AM FRIDAY...
HIGH PRESSURE AND VFR CONDITIONS EXPECTED THROUGH THE 06Z TAF
PERIOD. SURFACE WINDS SHOULD REMAIN WEST TO WEST NORTHWEST AT 10
KNOTS OR LESS... HIGHEST THIS AFTERNOON.
VFR TO CONTINUE OWING TO CONTINUED HIGH PRESSURE RIDGING THROUGH
SATURDAY. INITIALLY HIGH-MID LEVEL CEILINGS WILL LOWER TO LIFR/IFR
RANGE SATURDAY NIGHT AND CONTINUE THROUGH SUNDAY... IN RESPONSE TO
THE DEVELOPMENT AND PASSAGE OF A RAIN PRODUCING LOW PRESSURE
SYSTEM ALONG THE SOUTHEAST US COAST. WHILE THE RAIN AND CEILINGS
SHOULD EXIT BY SUNDAY NIGHT... A LIGHT WIND AND FRESHLY SATURATED
SOIL COULD LEAD TO THE DEVELOPMENT OF FOG LATE SUNDAY NIGHT AND
MONDAY MORNING. HIGH PRESSURE AND VFR CONDITIONS EXPECTED AGAIN
FOR THE EARLY PART OF THE UPCOMING WEEK.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...
NEAR TERM...
SHORT TERM...
LONG TERM...MWS
AVIATION...MWS
