FXUS62 KRAH 071144
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
645 AM EST MON DEC 7 2009
.SYNOPSIS...
COLD HIGH PRESSURE WILL MOVE OFFSHORE THROUGH EARLY THIS MORNING. A
WEAK LOW PRESSURE TROUGH WILL CROSS THE REGION LATE TODAY... THEN
ANOTHER HIGH PRESSURE AREA WILL BUILD OVER THE MID ATLANTIC REGION
THROUGH TONIGHT AND TUESDAY. A DEVELOPING STORM SYSTEM WILL APPROACH
FROM THE SOUTHWEST AND BRING WIDESPREAD RAIN FOR TUESDAY NIGHT...
FOLLOWED BY A CHANCE OF SHOWERS AND AN ISOLATED STORM ON
WEDNESDAY... AHEAD OF A COLD FRONT THAT WILL SWEEP THROUGH BY
WEDNESDAY EVENING.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 200 AM MONDAY...
FOR TODAY THROUGH TONIGHT: A MINOR SHORTWAVE NOW OVER THE CENTRAL
CAROLINAS WILL MOVE OFF THE COAST BY MORNING... TAKING THE SHROUD OF
HIGH CLOUDS NOW OVER EASTERN NC WITH IT. BUT A BATCH OF WARM
ADVECTION MID CLOUDS OVER THE LOWER MISS VALLEY AND MIDSOUTH WILL
PUSH OVER THE CWA THIS AFTERNOON. MEANWHILE... THE CHILLY SURFACE
HIGH NOW CENTERED OVER DELMARVA WILL CONTINUE ITS EASTWARD DRIFT OFF
THE COAST TODAY. AS IT DEPARTS... 925-850 MB WARM FRONT SHIFTS
NORTH-NORTHWEST INTO THE CWA... PULLING IN ENOUGH LOW LEVEL MOISTURE
(NOW EVIDENT OVER EASTERN/SOUTHERN SC AND MUCH OF GA) FOR PARTLY TO
MOSTLY CLOUDY SKIES THROUGH MUCH OF TODAY. THE MODELS SHOW WEAK
ISENTROPIC UPGLIDE AT 285-295K ALONG/EAST OF INTERSTATE 95... BUT
THIS UPGLIDE IS WEAKER THAN YESTERDAY'S MODEL RUNS INDICATED... AND
LOW LEVEL MOISTURE TRANSPORT IS WEAK AS WELL. CURRENT FORECAST OF
SLIGHT CHANCE POPS IN THE FAR EASTERN CWA IS IN LINE WITH LATEST
GUIDANCE AND TRENDS AND THESE POPS WILL BE RETAINED. MINOR LOW LEVEL
WARMING IS EXPECTED WITH THE 925 MB WARM FRONT EDGING UP THROUGH THE
SOUTHEAST CWA... HOWEVER THE NEAR-SURFACE WARM ADVECTION IS VERY
WEAK AND LOW LEVEL THICKNESSES ARE NEAR TO JUST BELOW NORMAL WITH
VERY STABLE LOW LEVELS DUE TO THE RELATIVE MILD AIR OVERRUNNING THE
LINGERING COOL SURFACE AIR. SO FACTORING IN PERIODS OF CLOUDS...
EXPECT COOL HIGHS OF 49-54. A VERY WEAK TROUGH AT 925-850 MB SHIFTS
EAST THROUGH THE AREA EARLY TONIGHT... SHIFTING WINDS IN THE LOWEST
2 KM TO WEST-SOUTHWEST OR WEST BRIEFLY... BEFORE THE NEXT HIGH
PRESSURE AREA DRIFTS EASTWARD ACROSS THE OH VALLEY TO MD BY TUESDAY
MORNING WHILE RIDGING SOUTHWARD INTO CENTRAL NC. WITH THE MODELS
INDICATING THE WEAK 850 MB EAST-WEST FRONT HOLDING IN THE VICINITY
WITH A FAST WEST-SOUTHWEST MID LEVEL FLOW... WEAK PERTURBATIONS
WITHIN THIS FLOW... AND AREAS OF CLOUDS UPSTREAM... EXPECT PRIMARILY
PARTLY CLOUDY SKIES WITH BRIEF PERIODS OF MOSTLY CLOUDY SKIES
OVERNIGHT. SEE LITTLE REASON TO CHANGE CURRENT FORECAST LOWS OF
33-41. -GIH
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 255 AM MONDAY...
MODELS ARE IN GOOD AGREEMENT WITH TAKING A POTENT STORM SYSTEM OUT
OF THE FOUR CORNERS REGION ON TUESDAY MORNING... AND QUICKLY
TRACKING IT INTO THE GREAT LAKES REGION BY WEDNESDAY AFTERNOON.
MEANWHILE AT 1025 MB HIGH IS EXPECTED TO EXTEND INTO OUR REGION FROM
THE NORTH ON TUESDAY... AND BEGIN TO LIFT OFF TO THE NORTH AND
NORTHEAST ON TUESDAY NIGHT INTO WEDNESDAY MORNING AS THE PRIMARY
SURFACE LOW LIFTS NORTHEASTWARD OUT OF THE MIDWEST INTO THE GREAT
LAKES REGION. AS THIS HAPPENS LOW LEVEL FLOW JUST OFF THE SURFACE
WILL ACROSS OUR AREA WILL INCREASE ON TUESDAY AND BECOME
SOUTHERLY... RESULTING IN OVERCAST SKIES. EXPECT TUESDAY TO
GENERALLY BE DRY... WITH POSSIBLY SOME PATCHY RAIN DEVELOPING IN THE
WEST LATE IN THE DAY AS ISENTROPIC LIFT STARTS TO INCREASE.
AFTERNOON HIGH TEMPS LOOK TO BE ON THE CHILLY SIDE AGAIN... AS THE
COLD HIGH PRESSURE CENTER TO THE NORTH WILL CONTINUE TO ALLOW FOR A
CHILLY NORTH TO NORTHEASTERLY FLOW AT THE SURFACE TO CONTINUE.
THUS... EXPECT AFTERNOON HIGHS TO GENERALLY RANGE FROM THE MID 40S
ACROSS THE NORTHWEST TO THE LOWER TO MID 50S ACROSS THE SOUTHEAST.
IF THE PRECIP BEGINS TO MOVE IN FASTER THAN FORECAST... AFTERNOON
HIGHS WILL BE A BIT COOLER ACROSS THE WEST... AS WE WOULD LIKELY
WETBULB WITH TEMPS FALLING INTO THE LOWER 40S. ALSO... ALL PRECIP IS
EXPECTED TO REMAIN LIQUID FOR THIS EVENT.
HYBRID DAMMING EVENT WILL GET UNDER WAY ON TUESDAY NIGHT/WEDNESDAY
MORNING... AS ISENTROPIC LIFT ON THE 285K THROUGH THE 295K SURFACE
RAMPS UP AND 850MB WARM FRONT LIFTS THROUGH THE AREA AFTER 00Z... AS
850MB FLOW STRENGTHS TO 50 TO 60S KTS. QPF NOW LOOKS TO BE THE
HEAVIEST NORTH AND WEST OF THE TRIANGLE... AS THE BEST LARGE SCALE
ASCENT FROM THE ASSOCIATED UPPER LEVEL JET AND ISENTROPIC LIFT OCCUR
THERE. EXPECT ANYWHERE FROM 1 TO 1.5 INCHES OF RAIN POSSIBLE IN THE
NORTHWEST... TO LESS THAN A QUARTER OF AN INCH IN THE SOUTHEAST.
SURFACE WARM FRONT LOOKS TO MOVE THROUGH THE AREA FROM SOUTHEAST TO
NORTHWEST ON WEDNESDAY MORNING... AS THE STRONG SOUTHERLY FLOW
SCOURS OUT THE REMAINING STABLE WEDGE. THUS... WILL SHOW HOURLY
TEMPS RISING OVERNIGHT... FROM ACROSS THE THE SOUTHEAST AND
SPREADING THIS TREND NORTHWESTWARD WITH TIME. THUS... THIS WILL
CREATE QUITE A SPREAD IN TEMPS ACROSS THE AREA... WITH AN EXPECTED
SHARP TEMPERATURE GRADIENT ASSOCIATED WITH THE RETREATING WEDGE
BOUNDARY. OVERNIGHT LOWS LOOK TO RANGE FROM THE LOWER 40S ACROSS THE
NORTHWEST TO LOWER TO MID 50S ACROSS THE SOUTHEAST. KINEMATICS...
LIKE THE LAST SIGNIFICANT STORM SYSTEM LAST WEEK... LOOK STRONG
AGAIN... 0-1 KM HELICITY VALUE IN EXCESS OF 300 TO 400 MS/S2.
HOWEVER... OVERALL INSTABILITY AGAIN APPEARS TO BE LACKING. THUS...
SPC DAY 2 AND 3 CONVECTIVE OUTLOOKS (DAY 2 THROUGH 12Z WEDNESDAY...
AND DAY 3 BEYOND 12Z WEDNESDAY) HAS PORTIONS OF OUR CWA IN A "SEE
TEXT"... FOR THE POTENTIAL FOR ISOLATED TORNADOES AND DAMAGING WINDS
GUSTS. ACCORDINGLY... WE WILL NEED KEEP AN EYE ON THIS TREAT.
MID LEVEL DRY PUNCH WORKS INTO THE AREA FROM THE SOUTHWEST ON
WEDNESDAY BEFORE NOON... AS THE BEST LIFT SHIFTS TO THE NORTH AND
NORTHEAST OF THE AREA. THE COLD FRONT IS NOT EXPECTED TO CROSS THE
AREA UNTIL WEDNESDAY AFTERNOON INTO THE EVENING. THE ENTIRE AREA
SHOULD BE WARM SECTORED BY AROUND WEDNESDAY EARLY AFTERNOON AS GUSTY
SOUTHWESTERLY WINDS OF UP TO 20 TO 25 MPH... WITH WIND GUSTS OF UP
TO 35 MPH WILL BE POSSIBLE. THUS... WILL NEED TO KEEP AND EYE ON HOW
MUCH INSTABILITY WE HAVE... WITH MODELS CURRENTLY SHOWING 60+
DEWPOINTS SOUTH AND EAST OF THE TRIANGLE AREA... ALONG WITH
CONTINUED STRONG LOW LEVEL FLOW (UPWARDS OF 50 TO 60 KTS AT 850MB).
THUS... IF WE ARE ABLE TO GET ANY ENHANCEMENT WITH A BAND OF SHOWERS
ASSOCIATED WITH THE COLD FRONT... WE COULD POTENTIALLY GET SOME
DAMAGING WIND GUSTS. HIGH TEMPS ON WEDNESDAY SHOULD SOAR INTO THE
LOWER TO MID 60S NORTHWEST TO THE LOWER TO MID 70S SOUTHEAST.
WITH CAA UNDERWAY AND CLEARING SKIES ON WEDNESDAY NIGHT... EXPECT
TEMPS TO FALL INTO THE MID TO UPPER 30S ACROSS THE NORTHWEST TO
LOWER TO MID 40S ACROSS THE SOUTHEAST BY SUNRISE THURSDAY.
&&
.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 315 AM MONDAY...
COLD HIGH PRESSURE WILL BUILD INTO THE AREA ON THURSDAY AND SETTLE
ACROSS THE AREA ON FRIDAY. WITH AFTERNOON LOW LEVEL THICKNESS VALUES
PROGGED TO STRUGGLE TO MAKE IT TO 1300 METERS ACROSS MOST OF THE
CWA... EXPECT HIGH TEMPS WILL BE WELL BELOW NORMAL. HOWEVER... WILL
NOT GO OFF THE DEEP END WITH TEMPS YET... AS WE ARE STILL A WAYS OUT
IN THE FORECAST. THUS... WILL SHOW HIGH TEMPS RANGING FROM THE UPPER
40S ACROSS THE NORTH TO MID TO UPPER 50S ACROSS THE SOUTH FOR
THURSDAY WITH MOSTLY SUNNY SKIES AND STRONG DOWNSLOPE FLOW... WITH
AFTERNOON HIGH TEMPS ONLY RANGING FROM 45 TO 50 ACROSS THE AREA ON
FRIDAY WITH INCREASING CLOUD COVER. OVERNIGHT LOWS ON FRIDAY
MORNING... WILL BE QUITE COLD... WITH OVERNIGHT LOWS DROPPING INTO
(AT LEAST) THE MID TO UPPER 20S.
NEXT QUICK MOVING SYSTEM APPROACHES THE AREA ON FRIDAY NIGHT INTO
SATURDAY. THE GFS IS CONSIDERABLE FASTER THAN THE EC WITH THIS
FEATURE... WITH THE 00Z/07TH GFS SHOWING PRECIP FALLING ON FRIDAY
NIGHT INTO SATURDAY MORNING... WHILE THE 00Z/07TH EC HOLDS PRECIP
OFF UNTIL SATURDAY NIGHT/SUNDAY MORNING. WILL HAVE TO KEEP AN EYE ON
THIS SYSTEM AS THE GFS SHOWS LOW LEVEL THICKNESS VALUES IN A
POSSIBLE PROBLEMATIC AREA... POSSIBLE WINTERY PRECIP. HOWEVER...
GIVEN WE ARE STILL QUITE A WAYS OUT IN TIME AND LOTS OF MODEL RUN TO
RUN VARIABLE AND CONTINUITY OCCURRING... WILL LEAVE THE SATURDAY AND
SUNDAY FORECAST AS IS... BELOW NORMAL HIGHS WITH A CHANCE OF RAIN ON
SATURDAY.
&&
.AVIATION /12Z MONDAY THROUGH FRIDAY/...
AS OF 645 AM MONDAY...
VFR CONDITIONS WILL GENERALLY HOLD INTO THIS EVENING... ALTHOUGH
CIGS ARE EXPECTED TO DROP TO MVFR AT FAY TOWARD SUNSET. HIGH
PRESSURE AT THE SURFACE WILL SHIFT OFF THE MIDATLANTIC COAST... AND
THE SHIFT OF WINDS JUST OFF THE SURFACE TO A SOUTHEAST AND SOUTH
DIRECTION WILL PULL IN LOW LEVEL MOISTURE FROM EASTERN SC/GA/NORTH
FL NORTHWARD OVER EASTERN NC THIS AFTERNOON... THUS PRESENTING A
POTENTIAL FOR CLOUDS WITH BASES AT 1500-2500 FT TO GO BROKEN AT
FAY... AND POSSIBLY AT RWI AS WELL THIS AFTERNOON. MEANWHILE A FAST
FLOW ALOFT AND A SERIES OF WEAK DISTURBANCES WILL BRING OCCASIONAL
MID AND HIGH CLOUDS WITH BASES ABOVE 8 K FT THROUGH THIS EVENING...
AFFECTING ALL TERMINAL SITES. WINDS WILL REMAIN LIGHT... MAINLY
UNDER 6 KTS. VSBYS MAY DIP TO MVFR BRIEFLY THIS MORNING AND AGAIN
TONIGHT... BUT VSBYS AOA 6SM SHOULD PREVAIL FOR MUCH OF THE FORECAST
VALID PERIOD.
LOOKING BEYOND TONIGHT... WEAK HIGH PRESSURE SHIFTS OVER THE
MIDATLANTIC REGION AND OFFSHORE THROUGH TUESDAY... THEN A DEVELOPING
STORM SYSTEM AND ASSOCIATED WARM FRONT APPROACHING FROM THE
SOUTHWEST WILL BRING WIDESPREAD RAIN AND IFR/LIFR CONDITIONS FROM
SUNSET TUESDAY THROUGH DAYBREAK WEDNESDAY MORNING. BEHIND THE WARM
FRONT... THE LIFR/IFR CLOUDS BREAK UP A BIT TO BROKEN IFR/MVFR IN
THE WARM SECTOR AHEAD OF A COLD FRONT. BRISK AND GUSTY SOUTHWEST
WINDS SHOULD BRING CONSIDERABLE LOW LEVEL TURBULENCE ON WEDNESDAY.
THE COLD FRONT MOVES THROUGH LATE WEDNESDAY... AND VFR CONDITIONS
WILL RETURN FOR WEDNESDAY NIGHT INTO FRIDAY. -GIH
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...HARTFIELD
NEAR TERM...HARTFIELD
SHORT TERM...BSD
LONG TERM...BSD
AVIATION...HARTFIELD
