Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 282036
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
336 PM EST WED JAN 28 2015

.SYNOPSIS...HIGH PRESSURE WILL BUILD OVER THE REGION THROUGH EARLY
THURSDAY AND THEN OFF THE SOUTHEAST COAST THURSDAY AFTERNOON.  A
COLD FRONT WILL SWEEP THROUGH THE AREA LATE THURSDAY AND THURSDAY
NIGHT. COOL HIGH PRESSURE WILL BUILD BACK IN FROM THE WEST FRIDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 245 PM WEDNESDAY...

HIGH PRESSURE WAS CENTERED OVER THE OHIO VALLEY AT 19Z AND WILL
SHIFT OVER NC AND VA TONIGHT. THERE IS SOME REAL THIN CIRRUS
SPILLING OVER THE SHORTWAVE RIDGE OVER THE MIDWEST...BUT LOOKS WAY
TO THIN TO HAVE MUCH IMPACT ON LOWS AS IT ADVECTS TOWARD OUR REGION.
GIVEN THAT LOWS WERE IN THE 20S LAST NIGHT AND THERE HAS BEEN LITTLE
AIRMASS MODIFICATION TODAY...EXPECT TO SEE MORE LOWS IN THE LOW/MID
20S...POSSIBLY SOME TEENS IN OUTLYING AREAS.

&&

.SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
AS OF 255 PM WEDNESDAY...

THURSDAY...HIGH PRESSURE OVER THE AREA EARLY THURSDAY MORNING WILL
WEAKEN AND SHIFT SOUTHEAST OF THE SC COAST BY MIDDAY.  MEANWHILE...A PAIR OF
SHORTWAVES... ONE EMERGING OFF THE CENTRAL ROCKIES AND ANOTHER
DIVING SOUTH OUT OF THE CANADIAN ROCKIES WILL IMPACT THE REGION
THURSDAY AFTERNOON/NIGHT.  WITH THE LEAD WAVE...FORCING IS FOCUSED
ALOFT AS THE BRUNT OF THE DCVA PASSES TO OUR NORTH.  MOISTURE IS
FOCUSED IN THE MID-LEVELS...PER NAM/GFS BUFR SOUNDINGS...AND
DECREASES RAPIDLY WITH SOUTHWARD EXTENT.  WHILE THE ECMWF PRODUCES A
FEW HUNDREDTHS AREAWIDE BETWEEN 18-00Z...THE NAM/GFS/SREF SUGGEST
JUST A PASSING SPRINKLE AT BEST DURING THE AFTERNOON...AND THIS
LOOKS MOST REASONABLE. SOUTHERLY WIND WILL HELP HIGHS REBOUND
THURSDAY ESPECIALLY IN THE WEST...UPPER 40S NORTHEAST TO LOWER 50S
SOUTHWEST.

THURSDAY NIGHT...ON THE HEELS OF THE LEAD WAVE...THE TRAILING
SHORTWAVE...AND ASSOCIATED WEAK COLD FRONT...WILL CROSS THE CWA IN
THE 03-09Z TIME FRAME.  THE FORCING FOR ACCENT IS MUCH BETTER WITH
STRONGER DCVA AND WEAK LOW-LEVEL FRONTAL CONVERGENCE...ALL WITHIN
THE LEFT EXIT REGION OF A STRENGTHENING SPEED MAX OVER THE MID-
MISSISSIPPI VALLEY REGION.  HOWEVER...MOISTURE MAY AGAIN BE TOO
LIMITED AS THE DEEPER LAYER FLOW BECOMES WESTERLY.  A FEW ISOLATED
LIGHT SHOWERS OR SPRINKLES ARE POSSIBLE WITH FRONT...BUT MAJORITY OF
THE AREA SHOULD BE DRY. MAY SEE A FEW WIND GUSTS BEHIND THE FRONT
WITH THE INITIAL COLD ADVECTION...AS LOWS FALL INTO THE LOW TO MID
30S.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
AS OF 335 PM WEDNESDAY...

FRI THROUGH SAT NIGHT: THE MODELS ARE IN GOOD AGREEMENT REGARDING
THE AMPLIFICATION OF A PAIR OF STRONG NORTHERN STREAM SHORTWAVE
TROUGHS INTO AND OFFSHORE THE COAST OF THE MIDDLE ATLANTIC STATES ON
FRIDAY. THE ASSOCIATED SFC COLD FRONT SHOULD BE NEAR THE COAST AT
THE START OF THE PERIOD/12Z FRI...WITH STRONG CAA - OFFSET TO SOME
DEGREE BY 30 KTS OF NW DOWNSLOPE FLOW - FOR THE REMAINDER OF THE
DAY. THE RESULT WILL BE BLUSTERY NW WINDS TO AROUND 30 MPH WITHIN A
DEEPLY MIXED (~5 K FT) BOUNDARY LAYER...AND HIGHS IN THE MIDDLE 40S
TO AROUND 50 DEGREES.

1030 MB CONTINENTAL POLAR HIGH PRESSURE WILL BUILD EAST OF THE
APPALACHIANS FRI NIGHT. CONSENSUS LL THICKNESS VALUES AROUND 1280
METERS SUPPORT LOWS MOSTLY IN THE LOWER 20S...THOUGH UPPER TEENS
WILL BE POSSIBLE WHERE AND IF DECOUPLING/CALM OCCUR TOWARD DAYBREAK.

THE SFC RIDGE WILL CREST OVERHEAD SAT...THEN DRIFT OFFSHORE SAT
NIGHT. MEANWHILE ALOFT...INITIALLY NW FLOW WILL TRANSITION TO
INCREASINGLY ZONAL FLOW DOWNSTREAM OF BOTH A NORTHERN STREAM S/W
TROUGH APPROACHING FROM WESTERN CANADA AND AN EVOLVING UPPER LOW
NEAR THE BAJA. THE ZONAL FLOW WILL ALLOW ABUNDANT MID-HIGH LEVEL
MOISTURE TO STREAM EAST OVER CENTRAL NC LATE IN THE DAY AND
PARTICULARLY OVERNIGHT SAT. GIVEN THE INCREASING MOISTURE
ALOFT...LOWS WILL BE NOT BE AS COLD - MOSTLY IN THE LOWER (TO
PERHAPS MIDDLE) 30S. WHILE THE INCREASING MID-HIGH LEVEL MOISTURE
WILL LIKELY RESULT IN WIDESPREAD VIRGA BY EARLY SUN...A DRY SUB-
CLOUD LAYER IN EXCESS OF 7-8 THOUSAND FT PER MODEL CROSS SECTIONS
SUGGEST IT WILL REMAIN DRY AT THE SFC. *IF* LIFT AND MOISTURE WERE
TO INCREASE MORE QUICKLY THAN CURRENTLY FORECAST...PARTIAL THICKNESS
AND WET BULB PROFILE VALUES WOULD SUPPORT SNOW AT THE ONSET...BUT
PROSPECTS OF THAT HAPPENING ARE VERY LOW.

SUN THROUGH MON: THE MODELS HAVE TRENDED FLATTER WITH THE NORTHERN
STREAM S/W TROUGH (REFERENCED ABOVE) AS IT AMPLIFIES INTO THE MIDDLE
ATLANTIC STATES THROUGH SUN NIGHT OR MON. THE ASSOCIATED SFC LOW
REFLECTION IN RECENT NWP RUNS IS CONSEQUENTLY MUCH WEAKER AND MORE
SUPPRESSED THAN EARLIER FORECASTS. REGARDLESS OF WHETHER OR NOT THE
GUIDANCE TRENDS BACK TOWARD A STRONGER SYSTEM LIFTING UP WEST OF THE
APPALACHIANS...THE HIGHEST RAIN CHANCES WILL STILL BE SUNDAY NIGHT
IN EITHER SCENARIO. BEFOREHAND...SUNDAY SHOULD BE A CLOUDY DAY FOR
CENTRAL NC...WITH RAIN CHANCES INCREASING FROM TOP-DOWN SATURATION
OVER MAINLY THE WESTERN AND NORTHERN PIEDMONT...AND WITH HIGHS WELL
BELOW FULL SUN VALUES - MOSTLY IN THE MIDDLE 40S TO AROUND 50
DEGREES. THE FLATTER/WEAKER SFC SOLUTIONS DO HAVE RAMIFICATIONS ON
PRECIPITATION CHANCES AND TEMPERATURES FOR MON...HOWEVER...SUCH THAT
THE BULK OF THE DAY WOULD BE DRY BEHIND THE SYSTEM GIVEN THE LATEST
MODEL TRENDS...WITH CAA-DRIVEN TEMPERATURES IN THE MIDDLE 40S TO
AROUND 50 DEGREES.

MON NIGHT THROUGH WED: BENEATH HEIGHT RISES ALOFT BEHIND THE
DEPARTING NORTHERN STREAM S/W TROUGH...POST-FRONTAL...CONTINENTAL
POLAR HIGH PRESSURE WILL BUILD OVERHEAD MON NIGHT-TUE...THEN DRIFT
OFFSHORE TUE NIGHT-WED. MEANWHILE ALOFT...THE EVOLVING UPPER LOW
NEAR THE BAJA IS FORECAST TO EJECT AND TRACK ACROSS THE SOUTHERN
US...WITH ACCOMPANYING SFC LOW DEVELOPMENT FROM THE GOM TO THE
SOUTHEAST US COAST...THROUGH MID WEEK. THE RESULT WILL BE INCREASING
PRECIPITATION CHANCES IN CENTRAL NC...INTO THE SLIGHT TO CHANCE
RANGE...BY EARLY WED. PROJECTED PARTIAL THICKNESS VALUES WOULD
SUPPORT JUST A CHILLY RAIN.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
AS OF 1240 PM WEDNESDAY...

VFR CONDITIONS WILL CONTINUE THROUGH THE TAF PERIOD.  A FEW WIND
GUSTS OVER THE COASTAL PLAIN WILL SUBSIDE THIS AFTERNOON... WITH
WINDS TO GO CALM AFTER 00Z.  SOME HIGH CLOUDS WILL START TO SPREAD
BACK INTO THE AREA THURSDAY MORNING OUT AHEAD OF A SYSTEM MOVING
THROUGH THE MIDWEST.  HIGH PRESSURE OVER THE AREA WILL WEAKEN AND
MOVE OFFSHORE...GIVING WAY TO A SOUTH-SOUTHWESTERLY WIND THAT WILL
BE 5-10KT...STRONGER AT KGSO/KINT WHERE A FEW WINDS GUSTS INTO THE
15-20KT RANGE MAY DEVELOP DURING THE AFTERNOON.

OUTLOOK... A MOSTLY DRY COLD FRONT WILL MOVE THROUGH THE AREA
THURSDAY NIGHT.  A BRIEF PERIOD OF MVFR CEILINGS MAY ACCOMPANY THE
FRONT.  BREEZY NORTHWESTERLY WINDS WILL FOLLOW ON FRIDAY.  THE NEXT
PERIOD OF WIDESPREAD SUB-VFR CONDITIONS WILL LIKELY COME LATE SUNDAY
INTO MONDAY.


&&

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

&&

$$

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


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