Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 010755
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
253 AM EST SUN FEB 1 2015

.SYNOPSIS...HIGH PRESSURE OVER THE CAROLINAS WILL SHIFT OFFSHORE BY
MIDDAY. MOISTURE WILL OVERSPREAD THE AREA LATE TODAY AND TONIGHT IN
ADVANCE OF A DEEPENING LOW PRESSURE SYSTEM AND ASSOCIATED COLD FRONT
THROUGH THE AREA MONDAY MORNING. DRY HIGH PRESSURE RETURNS ON
TUESDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 250 AM SUNDAY...

TODAY: MINOR MID-LEVEL IMPULSES IN ADVANCE OF THE NORTHERN STREAM
TROUGH AMPLIFYING OVER THE CENTRAL PLAINS WILL MOVE EAST ACROSS THE
REGION TODAY. ASSOCIATED WEAK DPVA WILL HELP TO MAINTAIN EXTENSIVE
MID/HIGH LEVEL CLOUDINESS OVER THE AREA TODAY. WHILE THE BLANKET OF
MID/HIGH CLOUDS WILL TEMPER INSOLATION A BIT...SOUTHERLY RETURN FLOW
AS THE HIGH PRESSURE SHIFTS OFFSHORE LATER THIS MORNING SHOULD AID
IN BOOSTING TEMPERATURES A GOOD 4 TO 7 DEGREES WARMER THAN
YESTERDAY. HIGHS IN THE LOWER TO MID 50S NORTH TO MID/UPPER 50S
SOUTH.

TONIGHT: AFOREMENTIONED NORTHERN STREAM TROUGH WILL ADVANCE E-SEWD
INTO THE OH/TN VALLEYS OVERNIGHT. ASSOCIATED DEEPENING SURFACE
LOW...LOCATED ALONG THE LEADING EDGE OF INTENSE 180-200 H5
FALLS...WILL TRACK EWD ALONG THE MASON-DIXON LINE ...MOVING INTO THE
MID ATLANTIC STATES MONDAY MORNING. STRONG DEEP MOISTURE TRANSPORT
IN ADVANCE OF THE FRONT...WITHIN THE STRENGTHENING 60-65KT SOUTHERLY
LLJ...WILL SUPPORT A 4-6 HOUR WINDOW OF CATEGORICAL POPS AS AN
EASTWARD BAND OF SHOWERS MOVE EAST ACROSS  THE AREA SUNDAY NIGHT-
MONDAY MORNING BETWEEN 06Z IN THE WEST TO 15Z IN THE EAST. QPF
AMOUNTS LOOK TO BE IN THE 0.25-0.50" RANGE... LIMITED BY THE
INTRUSION OF A MID-LEVEL DRY AIR RACING IN FROM THE WEST. MODELS
CONTINUE TO INDICATE MODEST MID-LEVEL LAPSE RATES ~6.5 C/KM WITH
MUCAPE OF ONLY 100-150 J/KG ACROSS SOUTHERN/EASTERN PORTIONS OF THE
FORECAST AREA...AND THUS VERY LOW PROBABILITY FOR SOME ELEVATED
THUNDER.   EXPECT A NON-DIURNAL TEMP TREND...WITH LOWS OCCURRING
BEFORE MIDNIGHT BEFORE THE ARRIVAL OF THE RAIN AND STRONG WAA. LOWS
SUNDAY NIGHT IN THE MID 40S NORTHEAST TO LOWER 50S SOUTH.
...RISING INTO THE 50S THROUGH THE PREDAWN HOURS.

&&

.SHORT TERM /MONDAY AND MONDAY NIGHT/...
AS OF 250 AM SUNDAY...

DEEP MOISTURE PLUME EMBEDDED WITHIN THE SOUTHERLY LLJ WILL SHIFT
EAST AND OUT OF THE AREA AT OR SHORTLY AFTER 15Z MONDAY...WHICH
SHOULD MARK THE BACK EDGE OF THE WIDESPREAD/CATEGORICAL POPS...WITH
TRAILING SFC COLD FRONT AND LINGERING SMALL CHANCE OF SHOWERS
LAGGING A FEW HOURS AFTERWARD.

STRONG POST-FRONTAL DRY COLD AIR ADVECTION REGIME WILL RESULT IN
WEST TO EAST CLEARING AND BREEZY/WINDY CONDITIONS DURING THE
AFTERNOON AS BUFR SOUNDINGS INDICATE 35-40KTS AT THE TOP OF THE
MIXED LAYER AND 25-30KTS JUST OFF THE SURFACE. HIGHS MONDAY SHOULD
OCCUR AT OR BEFORE SOLAR NOON...RANGING FROM NEAR 50 NW TO UPPER
50S/NEAR 60 SE. TEMPERATURES WILL THEN FALL INTO THE 40S THROUGH
THE AFTERNOON AS CONTINENTAL POLAR HIGH PRESSURE BUILDS INTO THE
AREA MONDAY NIGHT AND INTO THE DAY ON TUESDAY. WINDS LOOK TO
DECOUPLE OVERNIGHT...ESPECIALLY IN THE WEST...WHICH SHOULD HELP FOR
A WIDE RANGE IN TEMPERATURES. LOWS TUESDAY MORNING IN THE LOWER TO
MID 20S...WITH UPPER TEENS POSSIBLE IN THE TYPICALLY COLDER
LOCATIONS ACROSS THE WESTERN PIEDMONT.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
AS OF 250 AM SUNDAY...

TUESDAY AND TUESDAY NIGHT...THE GUIDANCE HAS BEEN CONSISTENT MOVING
A MID-LEVEL SHORTWAVE ACROSS CENTRAL NORTH CAROLINA DURING THE
DAY...WITH THE LEFT EXIT REGION OF A 140KT 300MB JET MOVING THROUGH
THE AREA TUESDAY MORNING WITH A 500MB JET JUST TO OUR SOUTH. AHEAD
OF THE SHORTWAVE...AND IN VICINITY OF THE JETS ALOFT BOTH THE NAM
AND THE GFS PROVIDE FOR SOME MOSTLY MID-LEVEL CLOUDINESS TUESDAY
MORNING WITH COLUMN DRYING TO FOLLOW FOR THE AFTERNOON. CENTRAL
NORTH CAROLINA IS IN AN 850MB THETA-E TROUGH WITH K INDICES
NEGATIVE...AND THE MOISTURE ALOFT DOES NOT CURRENTLY GET BELOW ABOUT
-20C AND THE AIR MASS BELOW THAT IS QUITE DRY. A PERIOD OF POSSIBLY
BROKEN CLOUDS IS ONLY ANTICIPATED EARLY TUESDAY BEFORE LATE MORNING
AND AFTERNOON INCREASING SUN. SUBSIDENCE TUESDAY NIGHT UNDER SURFACE
HIGH PRESSURE MOVING SOUTHEAST...WITH POSSIBLY A FEW CLOUDS
OVERNIGHT ASSOCIATED WITH THE RIGHT ENTRANCE REGION OF A 70KT 500MB
JET JUST TO OUR NORTH AND JUST MODEST MID-LEVEL MOISTURE. HIGHS
TUESDAY AND LOWS TUESDAY NIGHT BOTH ABOUT A CATEGORY BELOW
NORMAL...45 TO 50 FOR HIGHS TUESDAY AND MID TO UPPER 20S FOR LOWS
TUESDAY NIGHT.

WEDNESDAY THROUGH SATURDAY...PRIMARY CONCERN CONTINUES TO BE FOCUSED
ON THE SYSTEM FOR THURSDAY...AS A COLD FRONT APPROACHES WEDNESDAY
AND MOVES THROUGH MUCH IF NOT ALL OF CENTRAL NORTH CAROLINA
WEDNESDAY NIGHT WITH A SURFACE LOW MOVING OVER SOME PART OF THE
SOUTHEAST THURSDAY. THE GFS HAS TRENDED TOWARD THE PREVIOUS FEW
VERSIONS OF THE ECMWF...WITH A DEEPER MID-LEVEL TROUGH MOVING
SOUTHEAST ACROSS CANADA AND INTO THE GREAT LAKES WHICH SUPPRESSES
THE SURFACE AND MID-LEVEL LOW TRACKS SUCH THAT CENTRAL NORTH
CAROLINA WOULD RECEIVE LITTLE IF ANY PRECIPITATION. IT IS STILL
CLOSE...THOUGH...AND FOR WHAT THEY ARE WORTH THE CANADIAN AND THE
DGEX ARE STILL FARTHER NORTH AND WET FOR CENTRAL NORTH CAROLINA AT
LEAST FOR THURSDAY. THE HIGHER QPF MODELS HAVE PARTIAL THICKNESSES
THAT WOULD BE LIQUID ON THURSDAY FOR THE AREA...WHILE THE DRIER
GUIDANCE IS COLDER. THE GFS HAS CERTAINLY TRENDED THE COLDER
WAY...WITH HIGHS BY FRIDAY ON THE GFS MEX MOS GUIDANCE BARELY ABOVE
FREEZING IN THE TRIAD.

COMPLICATING THINGS...THE LATEST ECMWF IS SLOWER WITH THE TIMING OF
THE MID-LEVEL TROUGH MOVING OUT OF CANADA...WITH A CORRESPONDINGLY
SLOWER COLD FRONTAL PASSAGE AND A NOW SLIGHTLY FARTHER NORTH SURFACE
LOW TRACK. LIKE THE CANADIAN AND THE DGEX...THICKNESSES ARE WARM FOR
MUCH OF THURSDAY BEFORE COLDER AIR SETTLES IN. WHILE THE PROBABILITY
OF PRECIPITATION MAY...OVERALL...HAVE LEANED SLIGHTLY LOWER...WITH
THE OPERATIONAL GFS TRENDING PROGRESSIVELY DRIER IN EACH OF ITS LAST
FOUR RUNS...GFS ENSEMBLES ON THURSDAY STILL HAVE SOME MEMBERS WITH A
MORE MOIST AIR MASS AND PRECIPITATION. THE PRUDENT COURSE FOR
THURSDAY IS TO MAINTAIN SOME CHANCES WITH SLIGHT CHANCES WEST OF
ABOUT U.S. 1 AND CHANCES EAST...KEEPING PRECIPITATION LIQUID AND
CONFINED TO THURSDAY UNTIL OVERALL FEATURES RESOLVE THEMSELVES MORE
CLEARLY. THE WARMEST DAY SHOULD BE WEDNESDAY AHEAD OF THE COLD FRONT
WITH THICKNESSES AND THE CURRENTLY EXPECTED DEGREE OF ANY MID- AND
HIGH-LEVEL MOISTURE ALLOWING FOR HIGHS IN THE 50S. THERE HAVE BEEN
HUGE SWINGS IN MOS GUIDANCE HIGHS FOR THURSDAY...40S TO 50S AND BACK
AGAIN...AND 40S TO 50S TO 30S IN THE TRIAD ON PREVIOUS VERSIONS OF
THE ECMWF MOS. BY FRIDAY SOME CONFIDENCE THAT MOST HIGHS SHOULD BE
IN THE 30S MODERATING SOME FOR SATURDAY...BUT STILL BELOW NORMAL AND
MOSTLY IN THE 40S THEN...AS 1000-850MB THICKNESSES RISE 40M TO 50M
VERSUS VALUES OF AROUND 12Z FRIDAY.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
AS OF 1230 AM SUNDAY...

24-HR TAF PERIOD: HIGH PRESSURE CENTERED OVER THE AREA WILL SHIFT
OFF THE SE COAST THIS AFTERNOON...IN ADVANCE OF A POTENT UPPER LEVEL
WAVE AND ATTENDANT SFC LOW TRACKING EASTWARD FROM THE CENTRAL PLAINS
INTO THE OH VALLEY. THIS WILL SECURE VFR CONDITIONS THROUGH 21-00Z
WITH LIGHT VARIABLE WINDS BECOMING S/SW AT 10 TO 15KTS BY THE
AFTERNOON.  AS LOW-LEVEL MOISTURE INCREASES VIA STRENGTHENING
SOUTHERLY FLOW IN ADVANCE OF AN APPROACHING COLD FRONT. SHOWERS AND
MVFR/IFR CEILINGS WILL DEVELOP AT THE INT/GSO TERMINALS BETWEEN 00-
06Z MON...SPREADING EASTWARD ACROSS ALL THE AREA BETWEEN 06 TO 12Z.

LOOKING AHEAD: RAIN AND MVFR/IFR CEILINGS WILL SCATTER OUT WEST TO
EAST ACROSS THE AREA BETWEEN 15 TO 18Z AS THE FRONT EXITS THE AREA.
WINDY CONDITIONS ARE EXPECTED IN THE WAKE OF THE FRONT MONDAY
AFTERNOON WITH DANGEROUS W/NW CROSSWINDS WITH SUSTAINED WINDS OF 15
TO 20KTS AND GUSTS AS HIGH AS 35 KTS.  A NW BREEZE AT 10-15 KT WILL
PERSIST MON NIGHT AS HIGH PRESSURE BUILDS TOWARD THE REGION FROM THE
WEST. VFR CONDITIONS WILL RULE THROUGH MID-WEEK AS DRY HIGH PRESSURE
BUILDS OVER THE CAROLINAS.

&&

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

&&

$$

SYNOPSIS...CBL
NEAR TERM...CBL
SHORT TERM...CBL
LONG TERM...DJF
AVIATION...CBL/VINCENT


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