Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 311802
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
100 PM EST SAT JAN 31 2015

.SYNOPSIS...HIGH PRESSURE CONTINUES TO BUILD OVER THE REGION TODAY.
THE CENTER OF THE HIGH MOVES OFFSHORE TONIGHT AHEAD OF A LOW
PRESSURE SYSTEM THAT MOVES INTO THE MID-ATLANTIC MONDAY MORNING. THE
TRAILING COLD FRONT PUSHES EAST OF THE CAROLINAS MONDAY...FOLLOWED
BY HIGH PRESSURE AGAIN FOR THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /TODAY AND TONIGHT/...
AS OF 1030 AM SATURDAY...

LITTLE CHANGE TO THE FORECAST THIS MORNING.  STRONG MID-LEVEL
RIDGING AND SURFACE HIGH PRESSURE ENCOMPASSES MOST OF THE
SOUTHEASTERN QUARTER OF THE CONUS...WITH PW VALUES DOWN TO LESS THAN
0.15" ON MANY OF THE REGIONAL RAOBS.  MID/HIGH CLOUDS EXPANDING
ACROSS THE MID/LOWER MISSISSIPPI VALLEY SHOULD REMAIN MOSTLY WEST OF
THE AREA DURING THE DAY TODAY...WITH JUST A FEW PATCHES OF CIRRUS
OVER CENTRAL NC. FORECAST HIGHS ARE IN LINE WITH THE OBSERVED
MORNING 1000-850MB THICKNESS (1272M AT KGSO) AND SLIGHT RECOVERY
OVER THE SOUTHWEST AS THE SURFACE HIGH SHIFTS SOUTHEAST THIS
AFTERNOON.  MID 40S NORTHEAST TO AROUND 50 SOUTHWEST. -BLS

TEMPERATURES SHOULD FALL SOMEWHAT QUICKLY THIS EVENING THEN TEND TO
STABILIZE AS CLOUDS MOVE IN. LOWS TONIGHT 25 TO 30 NEAR AND EAST OF
INTERSTATE 95 AND AROUND 30 ELSEWHERE. MINIMUM RELATIVE HUMIDITIES
TODAY COULD FALL TO NEAR 15 PERCENT BASED ON THE EXPECTED SURFACE
DEW POINTS...BUT WINDS WILL BE MUCH LIGHTER COMPARED TO FRIDAY AND
BY THE TIME DEW POINTS WOULD FALL TO THOSE LEVELS THE FREQUENCY OF
ANY MODEST GUSTS SHOULD BE MUCH LOWER.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 300 AM SATURDAY...

SUNDAY: MINOR MID-LEVEL IMPULSES EMANATING FROM THE UPPER
TROUGH/CLOSED LOW OVER THE SOUTHWEST US WILL EJECT EASTWARD AND MOVE
THROUGH THE AREA IN ADVANCE OF THE NORTHERN STREAM TROUGH AMPLIFYING
OVER THE CENTRAL PLAINS. ASSOCIATED WEAK DPVA WILL RESULT IN
EXTENSIVE MID/HIGH LEVEL CLOUDINESS OVER THE AREA ON
SUNDAY...HOWEVER GRADUAL MOISTENING OF AN INITIALLY DRY ~10KFT SUB-
CLOUD LAYER LEFT(REMAINS OF THE MODERATING CP AIRMASS)WILL KEEP IT
DRY ACROSS MUCH OF CENTRAL NC DURING THE DAYLIGHT HOURS. THE
EXCEPTION WILL BE ACROSS THE FAR WESTERN ZONES WHERE A FEW SHOWERS
COULD DEVELOP LATE IN THE AFTERNOON AS THE WARM MOIST CONVEYOR FEED
BEGINS TO PUSH EAST OF THE MOUNTAINS. HIGHS SUNDAY IN THE LOWER 50S
NORTH TO MID 50S SOUTH.

SUNDAY NIGHT: AFOREMENTIONED NORTHERN STREAM TROUGH WILL CONTINUE TO
PROGRESS EASTWARD...REACHING THE SOUTHERN/CENTRAL APPALACHIANS BY
DAYBREAK MONDAY. DEEPENING SURFACE LOW....MOVING EASTWARD ALONG THE
LEADING EDGE OF THE ASSOCIATED 180-200 METER 500MB HEIGHT FALLS...
WILL TRACK ACROSS THE SOUTHERN OHIO VALLEY AND THROUGH THE
VIRGINIAS DURING THE PREDAWN HOURS...DRAGGING A SFC COLD FRONT INTO
THE NC FOOTHILLS. 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 ACROSS THE AREA SUNDAY NIGHT.
QPF AMOUNTS LOOK TO BE IN THE 0.25-0.50" RANGE...LIMITED BY THE
INTRUSION OF A MID-LEVEL SLOT RACING IN FROM THE WEST. HAVE NO PLANS
TO INCLUDE ANY THUNDER AT THIS TIME AS MODELS CONTINUE TO SHOW
MODEST MID-LEVEL LAPSE RATES (6.5-6.8 C/KM)WITH LESS THAN <200 J/KG
OF MUCAPE ACROSS THE AREA.

EXPECT A NON-DIURNAL TEMP TREND SUNDAY NIGHT...WITH LOWS OCCURRING
BEFORE MIDNIGHT...WITH TEMPERATURES THEN WARMING OVERNIGHT OWING TO
STRONG WAA. LOWS SUNDAY NIGHT IN THE MID 40S NORTHWEST TO LOWER 50S
SOUTH.

MONDAY AND MONDAY NIGHT: AGGRESSIVE MID-LEVEL DRY AIR INTRUSION WILL
OVERTAKE THE AREA FROM THE WEST BETWEEN 12 TO 18Z MONDAY IN ADVANCE
OF THE PASSAGE OF THE NORTHERN STREAM TROUGH PASSAGE MONDAY
AFTERNOON. THIS WILL BRING AN ABRUPT END TO PRECIP ACROSS THE AREA
MONDAY MORNING...WITH RAIN/SHOWERS EXITING THE COASTAL PLAIN DURING
THE MID TO LATE MORNING. EQUALLY IMPRESSIVE WILL BE STRONG POST-
FRONTAL DRY COLD AIR ADVECTION REGIME...WITH BREEZY/BLUSTERY
CONDITIONS AS BUFR SOUNDINGS INDICATING 38-40KTS AT THE TOP OF THE
MIXED LAYER(SIMILAR TO IF NOT STRONGER THAN THE GUSTS WE HAD
YESTERDAY). LOOK FOR TEMPERATURES FALLING THROUGH THE AFTERNOON AS
YET ANOTHER CP AIRMASS BUILDS INTO THE AREA MONDAY NIGHT AND INTO
THE DAY ON TUESDAY. MORNING HIGHS RANGING FROM MID UPPER 40S
NORTHWEST TO MID 50S SOUTHEAST. IF PROJECTED LOW-LEVEL THICKNESSES
AOA 1270M VERIFY AND WE DECOUPLE AS MODELS SUGGEST...EXPECT LOWS
TUESDAY MORNING IN THE LOWER 20S...WITH UPPER TEENS POSSIBLE IN THE
TYPICALLY COLDER LOCATIONS.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
AS OF 300 AM SATURDAY...

BOTH THE ECMWF AND THE GFS PASS A MID-LEVEL SHORTWAVE THROUGH
CENTRAL NORTH CAROLINA TUESDAY AS A BROAD...PROGRESSIVE TROUGH ALOFT
MOVES THROUGH. HOWEVER...WITH SURFACE HIGH PRESSURE IN PLACE AND
EXTENDING ACROSS THE GULF A PERIOD OF PARTLY TO POSSIBLY MOSTLY
CLOUDY SKIES SHOULD ONLY ACCOMPANY THE SHORTWAVE. AFTER EXPECTED
BRIEF CLEARING BEHIND THE MID-LEVEL WAVE...IN THE FAST AND SLOWLY
BACKING FLOW ALOFT BOTH THE ECMWF AND THE GFS FORECAST INCREASING
UPPER-LEVEL MOISTURE WEDNESDAY INTO WEDNESDAY NIGHT WITH A COLD
FRONT MOVING THROUGH WEDNESDAY NIGHT. BOTH THE GFS AND ECMWF ARE DRY
INTO THE OVERNIGHT HOURS OF WEDNESDAY WITH SURFACE HIGH PRESSURE
AHEAD OF THE COLD FRONT EXTENDING OVER THE GULF COAST AND LIMITING
LOW-LEVEL MOISTURE RETURN. FOR THIS FORECAST...WILL HAVE DRY
CONDITIONS TUESDAY INTO THE OVERNIGHT HOURS OF WEDNESDAY. MEX MOS
AND ECMWF MOS GUIDANCE POPS ARE BELOW CLIMATOLOGY DURING THIS PERIOD.

GUIDANCE DIFFERENCES ARE FAIRLY OBVIOUS BY LATE WEDNESDAY NIGHT.
MUCH WILL DEPEND ON HOW DEEP THE UPPER TROUGH MOVING THROUGH
SOUTHERN CANADA ENDS UP BEING DURING THE MIDDLE OF THE WEEK. THE
ECMWF HAS BEEN CONSISTENT OVER THE LAST COUPLE OF RUNS OR SO WITH A
DEEPER UPPER TROUGH EXTENDING THROUGH THE GREAT LAKES INTO THE OHIO
VALLEY. THIS SUPPRESSES THE TRACK OF AN UPPER LOW FORECAST BY BOTH
THE GFS AND THE ECMWF TO DEVELOP OVER OLD MEXICO...KEEPING DEEPER
MOISTURE TO OUR SOUTH AND RESULTING IN DRY CONDITIONS FOR CENTRAL
NORTH CAROLINA THROUGH THE END OF THE WEEK. THE GFS...ALSO
CONSISTENT WITH ITSELF...IS NOTICEABLY LESS AMPLIFIED WITH THE
CANADIAN UPPER TROUGH SUCH THAT THE WEAKENING UPPER LOW IS ABLE TO
MOVE TOWARD THE CAROLINAS BY THURSDAY ALONG WITH MORE MOISTURE. THE
GFS FORECASTS PRECIPITATION OVER CENTRAL NORTH CAROLINA BY 12Z
THURSDAY WHICH...IF IT OCCURS...WOULD BE LIQUID AS GFS PARTIAL
THICKNESSES ARE WELL INTO THE RAIN REGIME AT THAT TIME.

DUE TO THE GUIDANCE UNCERTAINTY...THE PRUDENT COURSE APPEARS TO BE
MAINTAINING CONSISTENCY WITH THE ONGOING FORECAST...A CHANCE OF RAIN
IN CENTRAL NORTH CAROLINA OVERNIGHT WEDNESDAY INTO THURSDAY WITH
CHANCES LOWEST AND BASICALLY NEAR SLIGHT IN THE TRIAD TO HIGHER
CHANCES ALONG AND EAST OF A LINE FROM ABOUT KMEB TO KRWI. IF THE GFS
VERIFIES EXACTLY THERE WOULD BE CONCERN ABOUT PRECIPITATION TYPE IN
THE LINGERING MOISTURE BY THURSDAY NIGHT...BUT A DRY ECMWF WITH NEAR
SOUTHEAST CONUS LOW PRESSURE MOVING OFFSHORE AND A DRY PREVIOUS
FORECAST WILL RESULT IN A DRY CURRENT FORECAST THURSDAY NIGHT
THROUGH FRIDAY NIGHT...THOUGH TURNING CHILLY AT THE END OF THE WEEK.

THE WARMEST DAY OF THE PERIOD SHOULD BE WEDNESDAY. 1000-850MB
THICKNESSES WOULD SUGGEST HIGHS AT LEAST IN THE MID TO UPPER 50S...
FAIRLY COINCIDENT WITH THE MEX AND MEE MOS GUIDANCE...BUT WILL LEAN
ABOUT A CATEGORY COOLER TOWARD THE HPC GUIDANCE FOR HIGHS IN THE
LOWER TO MID 50S DUE TO THE ANTICIPATED PRESENCE OF AT LEAST SOME
UPPER-LEVEL CLOUD COVER. THICKNESSES COOL AT THE END OF THE WEEK
AND...DESPITE DIFFERENCES IN OTHER DETAILS...1000-850MB
THICKNESSES...AND HPC AND MUCH OF THE MOS GUIDANCE...KEEP HIGHS ONLY
IN THE MID 30S TO LOWER 40S FRIDAY.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
AS OF 100 PM SATURDAY...

SKIES ARE CLEAR ACROSS CENTRAL NC THIS AFTERNOON WITH HIGH PRESSURE
ACROSS THE SOUTHEAST US.  WINDS WILL REMAIN LIGHT AND MOSTLY
VARIABLE OR WESTERLY THIS AFTERNOON.  INCREASING MID/HIGH CLOUDS OVER
THE CENTRAL US WILL SPREAD EAST TONIGHT BUT CEILINGS WILL REMAIN
ABOVE 10K FT.  HIGH PRESSURE WILL THEN SHIFT SOUTHEAST BY EARLY
SUNDAY AND WINDS WILL BECOME SOUTHWESTERLY DURING THE
DAY...INCREASING TO 8-12KT DURING THE AFTERNOON WITH A FEW GUSTS
TOWARD 20KT POSSIBLE AT MAINLY KGSO AND KINT.

OUTLOOK...CEILINGS WILL LOWER TO MVFR BY LATE SUNDAY AFTERNOON AND
EVENING AHEAD OF A LOW PRESSURE SYSTEM MOVING THROUGH THE
TENNESSEE/OHIO VALLEY.  RAIN WILL OVERSPREAD THE AREA SUNDAY
NIGHT...LIKELY CAUSING CEILINGS TO DROP TO IFR LEVELS...AS A STRONG
LOW-LEVEL JET SURGES ACROSS THE REGION. A COLD FRONT WILL THEN SWING
ACROSS CENTRAL NC ON MONDAY...WITH GUSTY NORTHWEST WINDS IN ITS WAKE
MONDAY AFTERNOON.  VFR CONDITIONS ARE THEN EXPECTED THROUGH MIDWEEK


&&

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

&&

$$

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


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