000
FXUS62 KRAH 202018
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
315 PM EST FRI NOV 20 2009

.SYNOPSIS...
HIGH PRESSURE WILL BUILD INTO CENTRAL NORTH CAROLINA FROM THE
NORTHWEST THROUGH TONIGHT. THE HIGH WILL DRIFT TO OUR NORTHEAST ON
SATURDAY... IN ADVANCE OF THE NEXT STORM SYSTEM WHICH WILL MOVE INTO
THE REGION FROM THE SOUTHWEST AND BRING CLOUDS AND RAIN FOR SUNDAY
AND SUNDAY NIGHT.

.NEAR TERM /THROUGH SATURDAY/...
AS OF 1235 PM FRIDAY...

FOR THE REST OF TODAY THROUGH TONIGHT THE LATEST SURFACE ANALYSIS
DEPICTS THE FRONT JUST OFF THE OUTER BANKS WITH THE INCOMING SURFACE
HIGH CENTERED OVER EASTERN KY. A DRY AND SUBSIDING COLUMN SHOULD
KEEP MOST AREAS RELATIVELY FREE FROM CLOUDS THROUGH THIS EVENING.
THE EXCEPTION IS OVER NORTHEAST NC WHERE A SURGE OF MOISTURE JUST
OFF THE SURFACE... NOTED WELL ON THE 12Z 925 MB ANALYSIS AND VISIBLE
SATELLITE IMAGERY... CONTINUES MOVING TOWARD THE SOUTH-SOUTHWEST
JUST AHEAD OF A SECONDARY LOW LEVEL COLD FRONT. THE 12Z/20 12KM NAM
SHOWED THIS FEATURE QUITE WELL... AND FAVORS PARTLY TO MOSTLY CLOUDY
SKIES SPREADING TO THE SOUTH-SOUTHWEST OVER EASTERN NC THROUGH THE
REST OF THIS AFTERNOON. FACTORING IN LOW LEVEL THICKNESSES... THE
CLOUDS IN THE EASTERN CWA... AND MOSTLY SUNNY SKIES ELSEWHERE...
STILL EXPECT HIGHS IN THE MID-UPPER 60S... COOLEST ACROSS THE NORTH
WHERE THE COLD AIR ADVECTION IS MOST PROFOUND. BEHIND THE SURGE OF
LOW LEVEL MOISTURE... SKIES SHOULD BE LARGELY CLOUD-FREE
OVERNIGHT... HOWEVER AS THE SURFACE HIGH SHIFTS UP INTO WV...
SURFACE WINDS IN NC SHOULD BECOME UNIFORM NORTHEASTERLY... AND GIVEN
THE MINOR AMOUNT OF RESIDUAL LOW LEVEL MOISTURE... THE UPSLOPE FLOW
AND RESULTANT LIFT/CONDENSATION COULD LEAD TO POCKETS OF STRATUS IN
THE EXTREME WESTERN CWA LATE TONIGHT. HIGH THIN CLOUDS BLOWING OFF
OF THE GULF COAST CONVECTION... ASSOCIATED WITH OUR NEXT STORM
SYSTEM... WILL START TO SPREAD SOUTHWEST TO NORTHEAST ACROSS THE
STATE LATE TONIGHT AS WELL. UNDER GENERALLY FAIR SKIES... STILL
EXPECT LOWS OF 39-46.

FOR SATURDAY THE MID LEVEL VORTEX DEEPENING OVER EASTERN TX/OK THIS
AFTERNOON MOVES SLOWLY ACROSS LA/MS THROUGH SATURDAY. MID-UPPER
LEVEL MOISTURE STEADILY INCREASES AND DEEPENS OVER NC... WHILE THE
SURFACE HIGH TO OUR NORTH CONTINUES MOVING NORTHWARD TO A POSITION
OVER LAKE ERIE... WHERE IT BEGINS TO BE SUPPORTED BY CONFLUENT FLOW
ALOFT WITH NORTHERN STREAM SHORTWAVE TROUGHING OVER PA... CAUSING
THE HIGH TO GRADUALLY STRENGTHEN. THIS PATTERN SHOULD ENSURE A
STEADY NORTHEASTERLY FEED OF LOW LEVEL DRY AIR INTO CENTRAL NC...
SETTING US UP FOR DAMMING ONCE THE SURFACE HIGH CAN GET INTO A MORE
FAVORABLE POSITION OVER THE ST LAWRENCE VALLEY SATURDAY NIGHT
WHERE IT CAN TAP INTO EVEN COOLER AIR AND STRENGTHEN FURTHER WITH
THE SUPPORT ALOFT PERSISTING. EXPECT STEADILY LOWERING AND
THICKENING CLOUDS THROUGH THE DAY... WITH A FEW LOWER STRATOCUMULUS
OVER THE WESTERN PIEDMONT WITHIN EASTERLY UPSLOPE LOW LEVEL FLOW.
BUT THE MOST ACTION WITH THIS SYSTEM ON SATURDAY WILL BE BANDS OF
CONVECTION OVER AL/GA AND THE NORTHEAST GULF... AND ANY SIGNIFICANT
FORCING TO GENERATE PRECIP OVER NC HOLDS OFF UNTIL AFTER SUNDOWN
SATURDAY WITH NO DISCERNIBLE ISENTROPIC UPGLIDE AND UPPER DIVERGENCE
HOLDING TO OUR SOUTH THROUGH THE DAY... PLUS THE SUBCLOUD LAYER AT
1-3 KM OVER NC REMAINS RATHER DRY. HIGHS 60-65 ARE SUPPORTED BY LOW
LEVEL THICKNESS TRENDS AND ARE NEAR THE LATEST STATISTICAL GUIDANCE.
-GIH

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
AS OF 315 PM FRIDAY...

THIS PORTION OF THE FORECAST WILL BE DRIVEN BY 1 A STRENGTHENING
TO NEAR 1028-1034 MB BUT MIGRATORY CAD SURFACE HIGH... 2 THE
APPROACH OF A DEAMPLIFYING BUT POWERFUL AND COMPLEX SOUTHERN STREAM
TROUGH ALOFT AND ATTENDANT UPPER JET LEFT EXIT REGION.... 3
CYCLOGENESIS ALONG THE LOW LEVEL BAROCLINIC ZONE OFFSHORE THE EAST
COAST SOUTHWESTWARD INTO THE WESTERN GULF OF MEXICO... AND 4
RESULTANT ISENTROPIC LIFT ATOP THE COLD DOME OVER INTERIOR NC.

THE OPERATIONAL MODELS ARE ALL OVER THE PLACE REGARDING THE
EVOLUTION OF THESE FEATURES AND RESULTANT TIMING OF THE UPCOMING
POTENTIAL RAIN EVENT OF AROUND A THIRD TO ONE INCH... HIGHLIGHTED BY
A FAST AND HEAVY OVER-THE-WESTERN PIEDMONT GFS LATE SATURDAY
NIGHT... AND THE TOTALLY DRY NAM FROM THE TRIANGLE NORTHWARD THROUGH
THE ENTIRE DAY SUNDAY. FORECAST CONFIDENCE IS ACCORDINGLY RELATIVELY
LOW... BUT WE WILL CONTINUE TO FAVOR THE TIMING OF THE PREVIOUS
FORECAST -- MOST CLOSELY RESEMBLING THE 12Z GEM -- WITH THE BULK OF
THE RAINFALL SUNDAY MORNING OVER THE SOUTHWEST... AND AREA WIDE BY
SUNDAY AFTERNOON AND SUNDAY NIGHT. FORECAST MAX TEMPERATURES SUNDAY
IN THE UPPER 40S NORTHWEST TO UPPER 50S SOUTHEAST COULD BE A FEW
DEGREES TOO COOL ESPECIALLY ACROSS THE NORTHERN AND EASTERN PORTION
OF THE CWA... GIVEN THE AFOREMENTIONED TIMING OF THE PRECIPITATION
SHIELD.

ALTHOUGH THE BULK OF THE PRECIPITATION SHOULD BE WINDING DOWN AND
LIFTING NORTHEASTWARD WITH THE COASTAL LOW... LOW CLOUDS AND DRIZZLE
IN NORTH OR NORTHEASTERLY LOW LEVEL FLOW ARE APT TO CONTINUE
THROUGHOUT THE DAY MONDAY AND PERHAPS INTO MONDAY NIGHT. HAVE
ACCORDINGLY REDUCED HIGH TEMPERATURES BY 4 TO 8 DEGREES INTO THE 56
TO 63 DEGREE RANGE FROM NORTH TO SOUTH.

.LONG TERM /TUESDAY THROUGH FRIDAY/...
AS OF 105 PM FRIDAY...

TUESDAY THROUGH WEDNESDAY ELONGATED SOUTHWEST TO NORTHEAST SURFACE
RIDGING... BENEATH BUILDING HEIGHTS IN SOUTHWESTERLY FLOW ALOFT
AHEAD OF AN EVOLVING CENTRAL AND EVENTUALLY EASTERN CONUS
TROUGH... SHOULD YIELD DRY AND ABOVE AVERAGE TEMPERATURES. HIGHS 62
TO 69... WARMEST TUESDAY. LOWS WITHIN A FEW DEGREES OF 45.

WEDNESDAY NIGHT THROUGH FRIDAY A SERIES OF INTENSE SHORTWAVE
TROUGHS ALOFT WILL HELP AMPLIFY THE AFOREMENTIONED UPPER TROUGH
ACROSS THE GREAT LAKES AND INTO THE NORTHEAST THROUGH THE REMAINDER
OF THE PERIOD. CYCLOGENESIS SHOULD ENSUE OFF THE EAST COAST... AS
THE UPPER FORCING APPROACHES THE BAROCLINIC ZONE JUST OFFSHORE.
ACCORDINGLY EXPECT PRECIPITATION CHANCES TO REMAIN SUPPRESSED TO THE
EAST OF CENTRAL NC... THOUGH THERE PROBABLY WILL BE PERIODS OF MID
AND HIGH CLOUDS ASSOCIATED WITH THE APPROACHING UPPER TROUGH/JET
AXIS... PARTICULARLY OVER THE EASTERN HALF OF THE STATE.
TEMPERATURES TREND DOWNWARD AS THE L/W TROUGH AXIS SETTLES IN BY
FRIDAY. HIGHS 60 TO 65 THURSDAY... WITH LOWER TO MIDDLE 50S EXPECTED
FOR FRIDAY. LOWS INTO THE 30S THURSDAY AND FRIDAY NIGHTS.

.AVIATION /17Z FRIDAY THROUGH WEDNESDAY/...
AS OF 1215 PM FRIDAY...

VFR CONDITIONS WITH UNRESTRICTED CIGS AND VSBYS ARE EXPECTED AT
INT/GSO/RDU/FAY THROUGH TONIGHT... HOWEVER AT RWI... MVFR CONDITIONS
WILL CONTINUE THROUGH MUCH OF THE AFTERNOON. THIS STRATUS IS
ASSOCIATED WITH A SECONDARY FRONT LOCATED A COUPLE THOUSAND FEET OFF
THE SURFACE OVER NORTHEAST NC DROPPING TOWARD THE SOUTH-SOUTHWEST.
SCATTERED MVFR-LEVEL CLOUDS MAY DRIFT NEAR RDU AND FAY THIS
AFTERNOON BUT ARE NOT EXPECTED TO BECOME BROKEN. OTHERWISE... NORTH
TO NORTHEAST WINDS SUSTAINED NEAR 10 KTS MAY PERIODICALLY GUST TO
15-18 KTS THROUGH 21Z. AFTER 21Z... AS THE SURFACE HIGH BUILDS IN
FROM THE NORTHWEST... THE PRESSURE GRADIENT OVER THE AREA WILL RELAX
RESULTING IN SUBSIDING WINDS. SKIES ARE EXPECTED TO BE MOSTLY CLEAR
AFTER SUNDOWN WITH UNRESTRICTED VSBYS AND NO CIGS... ALTHOUGH
SCATTERED CLOUDS AT 2 KFT TO 3 KFT ARE POSSIBLE AT INT/GSO AFTER
MIDNIGHT THROUGH DAYBREAK WITH WEAK UPSLOPE FLOW IN THE LOW LEVELS.
OTHERWISE CLOUD BASES SHOULD HOLD ABOVE 14 KFT THROUGH EARLY
SATURDAY AFTERNOON.

LOOKING BEYOND MIDDAY SATURDAY A STORM SYSTEM WILL APPROACH FROM
THE SOUTHWEST SATURDAY NIGHT/SUNDAY MORNING AND MAY BRING MVFR OR
IFR CONDITIONS TO THE REGION FOR SUNDAY THROUGH MONDAY. LOW CIGS ARE
EXPECTED TO CLEAR OUT BY MONDAY EVENING BUT AREAS OF IFR/LIFR FOG
MAY DEVELOP LATE MONDAY NIGHT/TUESDAY MORNING. VFR CONDITIONS ARE
ANTICIPATED TUESDAY MORNING THROUGH WEDNESDAY WITH HIGH PRESSURE
BUILDING IN FROM THE SOUTHWEST. -GIH

.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.

SYNOPSIS...HARTFIELD
NEAR TERM...HARTFIELD
SHORT TERM...MWS
LONG TERM...MWS
AVIATION...HARTFIELD