Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 010758
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
358 AM EDT WED APR 1 2015

.SYNOPSIS...A COLD FRONT WILL MOVE SOUTH THROUGH NC THIS MORNING.
COOL HIGH PRESSURE WILL FOLLOW FOR WED AND THU. A WARM FRONT MOVE
NORTH THROUGH THE REGION THU NIGHT...FOLLOWED BY THE PASSAGE OF A
STRONG COLD FRONT FRI NIGHT AND EARLY SAT.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 340 AM WEDNESDAY...

OBSERVATIONAL DATA INDICATE THE SFC COLD FRONT HAD MOVED INTO THE
SOUTHERN PIEDMONT/SANDHILLS/SOUTHERN COASTAL PLAIN AT 0730Z...AND
THE FRONT WILL CONTINUE TO MOVE SOUTH AND OUT OF NC THROUGH 12Z.
NORTH TO NE SFC WINDS WILL BE BRIEFLY GUSTY TO AROUND 15-20 KTS BOTH
IN THE FEW HOUR WAKE OF THE FRONT...AND AGAIN AS THE MIXED LAYER
DEEPENS WITH HEATING BETWEEN 12-15Z...MAINLY EAST OF 1-95.

WHILE A FEW PATCHES OF ALTOCUMULUS IN THE VICINITY OF THE FRONT WILL
DOT THE SKY THIS MORNING...IT WILL BE SHORT-LIVED AS THE PARENT S/W
TROUGH ALOFT MOVES AWAY FROM THE MIDDLE ATLANTIC COAST. CLEARING AND
HEIGHT RISES IN DEEP LAYER RIDGING ALOFT WILL FOLLOW...AND CAUSE A
1018 MB SFC HIGH OVER SOUTHERN OH TO STRENGTHEN A FEW MB AS IT
BUILDS SOUTHEASTWARD ACROSS VA/NC TODAY. ASSOCIATED NE FLOW WILL
RESULT IN COOLER (THAN TUE) TEMPERATURES...WITH DRY ADIABATIC MIXING
NEAR H85 SUPPORTIVE OF HIGHS IN THE LOWER 60S NE TO LOWER 70S SW.

SKIES WILL REMAIN CLEAR OR MOSTLY SO TONIGHT...WITH PERHAPS THE
SOUTHERN FRINGE OF CIRRUS IN NW FLOW ALOFT GRAZING THE NORTHERN
PIEDMONT THIS EVENING. H85-925 FLOW WILL BECOME SOUTHWESTERLY LATE
TONIGHT AS THE CENTER OF THE ANTI-CYCLONE IN THAT LAYER DRIFTS OFF
THE SC COAST...AND ASSOCIATED MOISTURE ADVECTION WILL CAUSE SOME
STRATOCUMULUS TO DEVELOP AND CREEP TOWARD THE YADKIN BY DAYBREAK.
BASED ON CURRENT AND PREVIOUS MODEL PROGS...IT IS UNLIKELY THAT THIS
CLOUD COVER WILL ARRIVE SOON OR THICK ENOUGH TO HAVE A LARGE IMPACT
ON OVERNIGHT TEMPERATURES. GIVEN THE RELATIVE CLEAR AND CONTINUED
NEARBY PRESENCE OF THE AFOREMENTIONED SFC HIGH NEAR THE VA/NC COAST
THAT GUIDANCE SUGGESTS WILL STRENGTHEN FURTHER BENEATH THE SUBSIDENT
RIDGING ALOFT (TO NEAR 1028 MB) GOOD TO EXCELLENT RADIATIONAL
COOLING CONDITIONS ARE EXPECTED...WITH PROJECTED LL THICKNESS VALUES
AROUND 1345 METERS AT 12Z THU SUPPORTIVE OF MIDDLE 30S TO AROUND 40
DEGREES - COOLEST EAST...NEARER THE CENTER OF THE SFC HIGH.

&&

.SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
AS OF 355 AM WEDNESDAY...

RETURN FLOW WILL DEVELOP AS THE PRECEDING SFC HIGH DRIFTS TOWARD
BERMUDA... AND THE MSL PRESSURE GRADIENT TIGHTENS DOWNSTREAM OF A
COLD FRONT APPROACHING FROM THE WEST - FROM THE LOWER GREAT LAKES TO
THE CENTRAL PLAINS. WARMING SOUTHERLY FLOW WILL CONSEQUENTLY RESULT
IN A RETURN OF TEMPERATURES IN THE 70S AREA-WIDE...EXCEPT PERHAPS
OVER THE NW PIEDMONT WHERE STRATOCUMULUS CENTERED AROUND H85
(REFERENCED IN THE NEAR TERM DISCUSSION) MAY RESULT IN MOSTLY CLOUDY
CONDITIONS.

THE PASSAGE OF A WARM FRONT AND ASSOCIATED THETA-E ADVECTION/
ISENTROPIC UPGLIDE THU NIGHT WILL CAUSE CLOUDS/STRATUS TO DEVELOP
THROUGHOUT CENTRAL NC OVERNIGHT...WITH MILD AND BREEZY AT TIMES
CONDITIONS...AND LOWS IN THE UPPER 50S TO LOWER 60S. BUFR SOUNDINGS
DEPICT THE RELATIVE DEEPEST SATURATION - IN THE LOWEST 5-6 THOUSAND
FT AND ENTIRELY ABOVE FREEZING - OVER THE WESTERN PIEDMONT...WHERE
PATCHY LIGHT RAIN OR DRIZZLE WILL BE POSSIBLE AND IS SUPPORTED BY A
SMATTERING OF A HUNDREDTH OR TWO QPF PER THE 00Z MODELS.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
AS OF 345 AM WEDNESDAY...

AN UPPER LEVEL DISTURBANCE CROSSING THE REGIN LATE THURSDAY WILL
MOVE OFF TO THE NORTHEAST FRIDAY MORNING...SUGGESTING A PERIOD OF
SUBSIDENCE IN ITS WAKE EARLY ON FRIDAY.  1000-850MB THICKNESSES ARE
PROGGED TO REACH 1390M FRIDAY AFTERNOON WITH A BREEZY SOUTHWEST FLOW
THAT MAY RESULT IN GUSTS TO 35-40MPH IF MIXING IS A DEEP AS GFS BUFR
SOUNDINGS SHOW.  SOME WEAK INSTABILITY IS EXPECTED WITH TEMPS
CLIMBING INTO THE UPPER 70S/LOWER80S AND DEWPOINTS IN THE LOWER 60S
OVER THE COASTAL PLAIN.  HOWEVER...THERE IS NO OBVIOUS FORCING
MECHANISM FOR CONVECTION...SO WILL KEEP JUST A SLIGHT CHANCE IN FOR
THE EASTERN CWA FRIDAY AFTERNOON.

BETTER FORCING FOR PRECIP IS EXPECTED FRIDAY NIGHT AND EARLY
SATURDAY WITH THE ARRIVAL OF A FAIRLY POTENT SHORTWAVE AND THE
ASSOCIATED DCVA AND COLD FRONT DIVING THROUGH THE MIDWEST.  MODELS
CONTINUE TREND SLOWER WITH THE FRONT AS A WAVE OF LOW PRESSURE MOVES
ALONG FRONT AND THROUGH THE OHIO VALLEY FRIDAY NIGHT.  THERE IS
STILL A SURPRISING AMOUNT OF MODEL DISCREPANCY REGARDING THE
STRENGTHEN AND TRACK OF THE SURFACE LOW...SO CONFIDENCE IN THE
TIMING OF THE FRONT IS STILL BELOW AVERAGE....BUT IN GENERAL THE
FRONT SHOULD NOT ARRIVE UNTIL AFTER MIDNIGHT. DESPITE STRONG
WESTERLIES AND DEEP LAYER SHEAR OF UP TO 40KT...WEAK LAPSE RATES AND
POOR DIURNAL TIMING SHOULD LIMIT THE FRONTAL CONVECTION TO TO MAINLY
SHOWERS.  WILL INDICATE LIKELY POPS LATE FRIDAY NIGHT AND EARLY
SATURDAY..WITH CLEARING CONDITIONS BY MIDDAY ON SATURDAY.  TEMPS
WILL BE WARM AHEAD OF THE FRONT AND MAY HOLD IN THE 60S FOR MUCH OF
THE AREA FRIDAY NIGHT...WITH HIGHS ON SATURDAY KNOCKED BACK TO NEAR
NORMAL BEHIND THE FRONT.

MODIFIED HIGH PRESSURE WILL BUILD OVERHEAD SATURDAY NIGHT...WHEN
1000-850 MB THICKNESSES DROP TO 1320M.  THIS SUGGESTS LOWS IN THE
MID 30S FOR MANY LOCATIONS AND A GOOD CHANCE AT SOME FROST.  A WARM
UP WILL THEN ENSUE ON SUNDAY AS THE HIGH MOVES OFFSHORE.  MOST OF
EARLY NEXT SHOULD BE DRY AS A SHORTWAVE CROSS THE GREAT LAKES AND WE
REMAIN JUST TO THE EAST OF THE BEST MOISTURE RETURN/INSTABILITY
ASSOCIATED WITH THE WARM SECTOR WEST OF THE MOUNTAINS.  HIGHS WILL
BE MOSTLY NEAR NORMAL.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
AS OF 210 AM WEDNESDAY...

VFR. A COLD FRONT AND ASSOCIATED WIND SHIFT TO NORTHERLY WITH
TEMPORARY GUSTINESS INTO THE MID TEENS TO NEAR 20 KTS...WILL
CONTINUE TO MOVE SOUTH THROUGH CENTRAL NC THIS MORNING. THE FRONT
HAD ALREADY CLEARED ALL BUT FAY AS OF THE 06Z TAF ISSUANCE...AND
FRONTAL PASSAGE THERE WILL BE BETWEEN 0730-08Z. WINDS WILL THEN
GRADUALLY VEER TO NE LATER THIS MORNING...WITH A BRIEF PERIOD OF
HIGHER SUSTAINED SPEEDS...AND GUSTS...THROUGH AROUND 15Z.
OTHERWISE...SKIES WILL BE MAINLY CLEAR...WITH THE EXCEPTION BEING A
BAND OF ALTOCUMULUS AND ASSOCIATED 8-11 THOUSAND FT CEILINGS IN THE
VICINITY OF THE FRONT THIS MORNING...AND PERIODS OF THIN CIRRUS
LATER TODAY AND TONIGHT.

OUTLOOK: THE PASSAGE OF A WARM FRONT WILL RESULT IN A GOOD CHANCE OF
MVFR-IFR CEILINGS THU NIGHT THROUGH EARLY FRI...WITH THE RELATIVELY
HIGHEST PROBABILITY OF OCCURRENCE AND LOWEST CEILINGS AT INT AND GSO.
A FEW SHOWERS WILL ALSO BE POSSIBLE DURING THAT TIME...ALSO MAINLY
AT INT AND GSO. WARM AND WINDY FRI...WITH SUSTAINED SW WINDS NEAR 20
KTS AND GUSTS 30-35 KTS...FOLLOWED BY SUB-VFR CONDITIONS AND
WIDESPREAD SHOWERS IN ASSOCIATION WITH A PASSING COLD FRONT...FRI
NIGHT AND EARLY SAT.

&&

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

&&

$$

SYNOPSIS...RAH
NEAR TERM...RAH
SHORT TERM...RAH
LONG TERM...22
AVIATION...RAH


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