-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 150622
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
222 AM EDT SAT MAR 15 2014

.SYNOPSIS...
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HIGH PRESSURE OVER THE SOUTHEAST STATES WILL DRIFT
OFFSHORE TODAY...IN ADVANCE OF A COLD FRONT THAT WILL SETTLE SOUTH
THROUGH THE CAROLINAS TONIGHT. MEANWHILE...LOW PRESSURE WILL DEVELOP
OVER THE CENTRAL PLAINS...THEN TRACK EASTWARD ALONG THE NORTHERN
GULF COAST STATES AND COASTAL CAROLINAS SUNDAY AND SUNDAY NIGHT.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH SATURDAY NIGHT/...
AS OF 1000 PM FRIDAY...

TONIGHT: A SHORTWAVE TROUGH TRACKING EAST ACROSS THE GREAT LAKES
THIS EVENING WILL PROGRESS INTO PORTIONS OF NEW ENGLAND AND THE
NORTHERN MID-ATLANTIC BY 12Z SAT. AN ATTENDANT SFC TROUGH WILL
EXTEND SOUTHWARD INTO THE CAROLINAS. ALTHOUGH EXTENSIVE MID-LEVEL
ECHOES /VIRGA/ AND A POTENTIAL FOR ISOLD SPRINKLES WILL BE
PRESENT...GIVEN THAT THE BEST DEEP-LAYER FORCING WILL REMAIN WELL
NORTH OF CENTRAL NC AND THAT VERY LITTLE LOW-LEVEL MOISTURE RETURN
IS PROGGED TO OCCUR OVERNIGHT...WILL CONTINUE TO INDICATE A DRY
FORECAST WITH THE THOUGHT THAT ANY SPRINKLES WOULD FALL UNDER THE
TRACE CATEGORY...AT BEST. GIVEN MID-LEVEL CLOUD COVER AND A LIGHT
SOUTHERLY BREEZE PERSISTING IN MOST AREAS...EXPECT LOWS IN THE LOWER
TO MID 40S. A FEW OF THE TYPICAL RURAL/LOW-LYING AREAS MAY SEE TEMPS
FALL IN THE UPPER 30S IF MOSTLY CLEAR SKIES AND CALM WINDS ARE
PRESENT A FEW HRS PRIOR TO SUNRISE. -VINCENT

SATURDAY AND SATURDAY NIGHT... BRIEF SHORTWAVE RIDGING AND A
WESTERLY WIND WILL ALLOW HIGHS TO CLIMB ANOTHER 10 DEGREES OR SO
INTO THE LOWER 70S ON SATURDAY.  HIGH CLOUDS WILL BEGIN TO POUR BACK
IN THE FROM THE WEST DURING THE EVENING HOURS AS SHORTWAVE BEGINS TO
EJECT OUR OF THE SOUTHWEST US AND THE SUBTROPICAL JET NOSES EASTWARD
ACROSS THE DEEP SOUTH.  MODELS INDICATE A WEAK UPPER DISTURBANCE
TRACK TOWARD THE AREA IN THE SOUTHWESTERLY FLOW ALOFT ON SATURDAY
NIGHT...BUT MOISTURE IS RATHER LIMITED UNTIL AFTER 12Z SUNDAY WHEN
AN 850MB MOVES INTO SC AND A ISENTROPIC LIFT BEGINS TO REALLY
INCREASE.  WILL MAINTAIN A SLIGHT CHANCE POP IN THE SOUTHERN
PIEDMONT KATE SATURDAY NIGHT...WITH LOWS IN THE 40S...WARMEST
SOUTHWEST.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
AS OF 235 PM FRIDAY...

FOR THIS PERIOD OF THE FORECAST...CURRENTLY A CHALLENGING FORECAST
WITH THE POTENTIAL FOR PRECIPITATION CAUSING SOME MAINSTEM RIVERS...
ALREADY HIGH...TO APPROACH MINOR FLOOD ESPECIALLY ON THE NEUSE...
AND FOR WINTRY WEATHER AS COLD AIR FILTERS INTO CENTRAL NORTH
CAROLINA MONDAY AND MONDAY NIGHT. MOISTURE AND LIFT DEEPEN SUNDAY
AND WHILE THE BEST CHANCES FOR PRECIPITATION EARLY SUNDAY SHOULD BE
IN THE SOUTHWEST PIEDMONT...THE CHANCES REALLY INCREASE QUICKLY TO
THE NORTHEAST DURING SUNDAY MORNING AND EARLY SUNDAY AFTERNOON AS
LIFT INCREASES ALONG WITH 850MB THETA-E VALUES. THE HIGHEST OF THESE
VALUES SUNDAY AFTERNOON AND SUNDAY NIGHT ARE CURRENTLY FORECAST IN
THE SOUTHWEST PIEDMONT...SANDHILLS...AND SOUTHERN COASTAL PLAIN...
WHERE THE HIGHEST PROBABILITY OF RAINFALL AT OR JUST OVER AN INCH
COULD OCCUR. BASED ON THE LATEST MMEFS HYDROLOGIC ENSEMBLES...WITH
THIS TYPE OF RAIN...AND THE RIVER LEVELS ALREADY RUNNING HIGH...
THERE IS A CHANCE OF RIVER LEVELS ON THE NEUSE...SUCH AS AT
CLAYTON...SMITHFIELD...AND GOLDSBORO...RISING BACK AND POSSIBLY
GETTING ABOVE THEIR MINOR FLOOD STAGES. THIS HAS BEEN NOTED IN THE
HWO. LATE SUNDAY AFTERNOON AND SUNDAY EVENING...GFS MUCAPE IN THE
LAYER FROM 1000-500MB REGISTERS SLIGHTLY IN THE FAR SOUTH TOWARD
KFAY AND KCTZ...AND THE GFS BUFR SOUNDING FROM KFAY NOTES A LAPSE
RATE NEAR MOIST ADIABATIC SUNDAY EVENING. WHILE A RUMBLE OF THUNDER
IS POSSIBLE...CAPE ON THE BUFR SOUNDING AT KFAY IS ONLY INTO DOUBLE
FIGURES...AND WILL LEAVE OUT OF THE FORECAST FOR NOW.

SUNDAY NIGHT INTO MONDAY...IT APPEARS THE GFS AND THE LATEST ECMWF
ARE TRENDING COLDER...AND WILL NEED TO WATCH THE TRACK OF THE SYSTEM
AND THE DEGREE OF COLD AIR INFILTRATION INTO CENTRAL NORTH CAROLINA
WITH REGARD TO PRECIPITATION TYPE. PARTIAL THICKNESSES WOULD SUGGEST
ALL LIQUID THROUGH 12Z MONDAY...THEN THESE THICKNESSES BECOME
SURFACE TEMPERATURE DEPENDENT AS THEY MOVE INTO THE FREEZING RAIN
CATEGORY MONDAY MORNING. ANTICIPATING ABOVE FREEZING TEMPERATURES
THROUGH MONDAY MORNING...WILL CONTINUE TO KEEP THE PRECIPITATION
TYPE ALL LIQUID THROUGH MONDAY MORNING. AFTER THAT...PARTIAL
THICKNESSES CONTINUE TO FALL...AND SREF ENSEMBLES ON BUFKIT
SOUNDINGS BECOME MORE NOTICEABLY WINTRY OVER THE NORTHWEST PIEDMONT
IN PARTICULAR. IN THAT AREA...FOR NOW IN THE GRIDDED FORECASTS WILL
HAVE THE LIKELIHOOD OF RAIN WITH A CHANCE OF SNOW BY MONDAY
AFTERNOON. FARTHER SOUTH AND EAST...THE PROBABILITY OF ANYTHING NON-
LIQUID SEEMS TOO LOW AT THE MOMENT...PARTICULARLY BASED ON THE
PREPONDERANCE OF THE SREF SOUNDINGS SUCH AS AT KRDU. SURFACE
TEMPERATURES SHOULD STAY ABOVE FREEZING THROUGHOUT CENTRAL NORTH
CAROLINA THROUGHOUT THE DAY. AFTER OVERNIGHT LOWS SUNDAY NIGHT FROM
THE MID 30S NORTHWEST TO THE MID 40S FAR SOUTHEAST...DAYTIME HIGHS
MONDAY SHOULD RECOVER LITTLE...FOR HIGHS IN THE UPPER 30S NORTHWEST
TO LOWER 50S FAR SOUTHEAST.

THE UPPER TROUGH MOVES THROUGH CENTRAL NORTH CAROLINA MONDAY NIGHT
AND EARLY TUESDAY AS THE SURFACE LOW BEGINS TO MOVE AWAY FROM
CENTRAL NORTH CAROLINA OFFSHORE AND OUT INTO THE ATLANTIC. THE
TIMING DIFFERENCES BETWEEN THE GFS AND ECMWF SEEM MODEST...AND FOR
THE WEATHER MONDAY NIGHT INTO EARLY TUESDAY WILL NEED TO WATCH HOW
THE DRYING IN THE MID LEVELS...COMBINED WITH COOLING THICKNESSES AND
TEMPERATURES...WITH LIGHTER QPF...AFFECT PRECIPITATION TYPE. AS
THICKNESSES AND SURFACE WET BULB TEMPERATURES COOL...COARSE MODEL
SOUNDINGS DRY ALOFT...SUCH THAT WHILE THERE IS THE POTENTIAL FOR
LIQUID PRECIPITATION TO MIX WITH OR CHANGE TO FROZEN PRECIPITATION
BEFORE ENDING...THE MAIN IMPACT COULD END UP BEING LINGERING
MOISTURE ON UNTREATED SURFACES FREEZING LATE MONDAY NIGHT INTO
TUESDAY MORNING AS TEMPERATURES OVER MOST OF CENTRAL NORTH CAROLINA
WEST OF A LINE FROM ABOUT KRWI TO KMEB FALL BELOW FREEZING. BASED ON
THE LATEST TIMING...ANY PRECIPITATION ENDS TUESDAY MORNING AS BROAD
RIDGING ALOFT MOVES IN QUICKLY FROM THE WEST. DAYTIME HIGHS ON
TUESDAY SHOULD BE ABOUT 10 TO 15 DEGREES BELOW NORMAL FOR MID MARCH.
THIS CORRESPONDS WELL WITH A FORECAST BLEND OF 1000-850MB
THICKNESSES...AND GFS MOS AND ECMWF ENSEMBLE MOS GUIDANCE. OVERALL...
HAVE UPDATED THE HWO TO SHOW THE POTENTIAL FOR WINTRY WEATHER AND...
AGAIN...TO NOTE THE POTENTIAL FOR HIGH WATER ON MAINSTEM RIVERS WITH
A FOCUS...BASED ON THE MMEFS...CURRENTLY ON THE NEUSE.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
AS OF 235 PM FRIDAY...

DIFFERENCES IN THE LONG-TERM GUIDANCE INCREASE FOR THE MIDDLE AND
END OF THE WEEK...MOSTLY WITH REGARD TO THE TIMING OF THE NEXT FRONT
AS STRONG LOW PRESSURE MOVES INTO THE GREAT LAKES. THE GFS IS FASTER
AND FOR THIS FORECAST WILL LEAN TOWARD THE SLOWER ECMWF...BASED
PRIMARILY ON THE STRENGTH OF THE LOW PRESSURE SYSTEM WHICH SHOULD
RESULT IN HIGHER AMPLITUDE ALOFT AND A SLOWER APPROACH...ESPECIALLY
ON THE HEELS OF A RECENTLY-DEPARTING SYSTEM. HAVE NOT COMPLETELY
TAKEN AWAY SLIGHT CHANCES FOR PRECIPITATION WEDNESDAY BUT CONFINED
THEM TO THE FAR WESTERN PIEDMONT FOR NOW...WITH CHANCES FOR SHOWERS
INCREASING ACROSS THE AREA OVERNIGHT WEDNESDAY INTO THURSDAY BEFORE
ENDING AS THE ECMWF 850MB FRONT MOVES EAST OF CENTRAL NORTH CAROLINA
DURING THURSDAY AFTERNOON. WHILE A SECONDARY TROUGH AND ANOTHER WEAK
COLD FRONT MAY MOVE THROUGH CENTRAL NORTH CAROLINA LATE IN THE
WEEK...SURFACE RIDGING OVER THE GULF AND...FOR NOW...NO STRONG MID-
LEVEL SHORTWAVE MOVING INTO CENTRAL NORTH CAROLINA IN THE NORTHWEST
FLOW ALOFT KEEP THE FORECAST DRY FROM THURSDAY NIGHT THROUGH FRIDAY.

THE TEMPERATURE FORECAST IS CHALLENGING FOR THE MIDDLE OF THE WEEK
AS THE ECMWF RETURNS A SOUTHERLY FLOW QUICKLY TO THE AREA
WEDNESDAY...WITH A NOTICEABLE INCREASE IN 850MB WINDS EAST OF THE
DEVELOPING LOW OFF TO OUR WEST AND NORTHWEST. SOME OF THE ECMWF
ENSEMBLES PUSH TEMPERATURES WEDNESDAY INTO THE 70S...THOUGH THE GFS
ENSEMBLES ARE NOTICEABLY COOLER. FOR THIS FORECAST WILL STAY CLOSE
TO THE ECMWF ENSEMBLE MEAN NOT JUST FOR WEDNESDAY...BUT THROUGH THE
END OF THE WEEK...RESULTING IN OVERALL TEMPERATURES NEAR NORMAL. THE
DIURNAL SPREAD SHOULD INCREASE LATE IN THE WEEK WITH DRIER BOUNDARY
LAYER AIR UNDER BROAD HIGH PRESSURE OUTSIDE OF ANY WEAK SURFACE
TROUGH OR FRONT.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
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AS OF 215 AM SATURDAY...

VFR. AN UPPER LEVEL DISTURBANCE AND ACCOMPANYING BAND OF MID AND
HIGH CLOUDS WILL MOVE OFFSHORE THIS MORNING. DRY DEEP LAYER WESTERLY
FLOW WILL FOLLOW FOR THE REMAINDER OF THE TAF PERIOD. AN UPPER JET
AXIS ALONG THE NORTHERN GULF COAST STATES WILL CAUSE CIRRUS TO
STREAK EASTWARD ACROSS MAINLY SOUTHERN NC TODAY...FOLLOWED BY
THICKENING AND LOWERING MID-HIGH CLOUDS FROM THE SOUTHWEST LATE
TONIGHT...AS THE FLOW ALOFT BUCKLES/BACKS TO SW IN RESPONSE TO A
STORM SYSTEM FORECAST TO DEVELOP OVER THE PLAINS STATES. WESTERLY
SURFACE WINDS WILL GUST TO BETWEEN 15-20 KTS WITH AS THE BOUNDARY
LAYER DEEPENS WITH HEATING THIS AFTERNOON.

OUTLOOK: WIDESPREAD ADVERSE AVIATION CONDITIONS ARE EXPECTED SUNDAY
THROUGH EARLY NEXT WEEK...IN ASSOCIATION WITH A COMPLEX LOW PRESSURE
SYSTEM FORECAST TO TRACK ACROSS THE GULF COAST STATES AND CAROLINAS.
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...MWS
NEAR TERM...VINCENT/SMITH
SHORT TERM...DJF
LONG TERM...DJF
AVIATION...MWS