Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 031151
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
650 AM EST WED FEB 03 2016

.SYNOPSIS...A WARM FRONT WILL LIFT NORTHWARD THROUGH NORTH CAROLINA
THIS MORNING. A COLD FRONT WILL CROSS THE REGION LATE THIS AFTERNOON
THROUGH TONIGHT... THEN SHIFT SLOWLY OFF THE COAST LATE THURSDAY.
HIGH PRESSURE WILL BUILD IN FROM THE WEST FRIDAY THROUGH SATURDAY.

&&

.NEAR TERM /TODAY THROUGH TONIGHT/...
AS OF 315 AM WEDNESDAY...

PRIMARY CONCERNS TODAY ARE THE RISK OF A FEW STRONG TO SEVERE
STORMS... AND THE ONSET OF STEADY MODERATE TO BRIEFLY HEAVY RAIN
THAT MAY PRESENT A THREAT OF RISING CREEKS AND URBAN FLOODING.

OVERVIEW: THE LATEST SURFACE MAP DEPICTS THE WARM FRONT JUST SOUTH
OF THE CWA AS THE PARENT HIGH CENTERED OVER THE CANADIAN MARITIMES
CONTINUES TO PROGRESS EASTWARD... LEADING TO A WEAKENING STABLE POOL
OVER CENTRAL NC. GIVEN THE VULNERABILITY OF THE WEAK WEDGE... THE
WARM FRONT SHOULD HAVE LITTLE TROUBLE TRACKING TO THE N/NNW THIS
MORNING... OVERTAKING THE TRIAD AREA BY MID MORNING. PATCHY VERY
LIGHT SHOWERS ARE POSSIBLE IN THE NW PIEDMONT THROUGH MID MORNING...
HOWEVER BASED ON THE CURRENT TRENDS AND LATEST HI-RES MODEL
OUTPUT... THE MORE SUBSTANTIAL AND WIDESPREAD SHOWERS AND STORMS
WILL BE SLOWER TO ARRIVE. A BATCH OF LIGHT RAIN PRECEDING THE
CONVECTION IS EXPECTED TO TRACK FROM CENTRAL GA NNE INTO THE SRN AND
WRN CWA DURING THE LATE MORNING... FOLLOWED BY A SLOW WEST-TO-EAST
MOVEMENT OF THE BROAD CONVECTIVE BAND THROUGH WRN AND CENTRAL NC
THIS AFTERNOON THROUGH EARLY EVENING... AND INTO ERN NC OVERNIGHT.
GIVEN THAT THE MID LEVEL STEERING FLOW WILL REMAIN LARGELY PARALLEL
TO THE SURFACE FRONT TODAY/TONIGHT... THE SLOWER MOVEMENT OF THE
FRONT AND ITS ASSOCIATED RAIN AS INDICATED BY THE WRF/ECMWF/3 KM
NAMRR/NSSL-WRF IS PREFERRED. WILL BRING IN LIKELY/CATEGORICAL POPS
MOSTLY AFTER SUNRISE THIS MORNING WEST OF HIGHWAY 1... THEN EXPAND
CATEGORICAL POPS EASTWARD OVER THE ENTIRE FORECAST AREA DURING THE
AFTERNOON INTO THE EVENING... BEFORE SHIFTING THESE HIGH POPS TO
JUST THE CENTRAL/ERN CWA OVERNIGHT.

QPF: THE POTENTIAL FOR MODERATE TO PERIODICALLY HEAVY RAIN
REMAINS... WITH PROJECTIONS OF DEEP LCL-TO-0C LAYERS NEAR 3.8 KM
FAVORING WARM RAIN PROCESSES... AND PW VALUES WELL OVER 1.5
INCHES... WHICH IF IT OCCURS WOULD APPROACH OR EXCEED RECORD PW
VALUES FOR THIS TIME OF YEAR. THE LONGER DURATION OF RAINFALL WITH
TRAINING WILL ALSO PUSH UP RAINFALL TOTALS. WHILE DYNAMIC FORCING
FOR ASCENT WILL BE LIMITED WITH LITTLE TO NO DPVA... THE KINEMATICS
ARE IMPRESSIVE WITH A 50+ KT LOW LEVEL JET CORRESPONDING TO THE
CONVECTIVE BAND... AND STRENGTHENING UPPER DIVERGENCE THIS AFTERNOON
INTO THE EVENING. EXPECT STORM TOTAL RAINFALL OF 1-2 INCHES... AND
PERHAPS HIGHER OVER THE EASTERN CWA... WHICH IS LIKELY TO GENERATE
STREET FLOODING... HIGH WATER IN POOR DRAINAGE AREAS... AND NUMEROUS
SWOLLEN CREEKS AROUND THE AREA. AT THE MOMENT THE EXPECTED RAINFALL
APPEARS LIKELY TO HOLD BELOW FLASH FLOOD GUIDANCE VALUES... SO WILL
NOT ISSUE A FLASH FLOOD WATCH AT THIS TIME... HOWEVER WE WILL
MONITOR UPSTREAM RAINFALL TODAY TO ASSESS IF ONE MIGHT BE NEEDED
LATE TODAY OR TONIGHT.

SEVERE THREAT: INSTABILITY WILL BE TOUGH TO ACHIEVE GIVEN WHAT
SHOULD BE A LARGELY DRY ADIABATIC PROFILE... MADE MORE DIFFICULT BY
THE LACK OF HEATING... AND MUCAPE VALUES APPEAR LIKELY TO HOLD UNDER
500 J/KG. HOWEVER... THE WIND FIELDS ARE PRETTY DRAMATIC WITH
INCOMING 0-6 KM BULK SHEAR OF 60-80 KTS AND LARGE LOOPING
HODOGRAPHS. CONVECTION-ALLOWING GUIDANCE UNANIMOUSLY DEPICTS AN
ORGANIZED QLCS MOVING SLOWLY THROUGH THE AREA THIS AFTERNOON INTO
THIS EVENING... ALTHOUGH INDIVIDUAL CONVECTIVE ELEMENTS WILL BE
MOVING VERY QUICKLY TO THE N OR NNE. AN ISOLATED EMBEDDED BRIEF WEAK
TORNADO OR TWO IS CERTAINLY POSSIBLE IN THIS SORT OF PATTERN... AND
STRONG WIND GUSTS OVER 35 MPH MAY OCCUR WITH LITTLE MORE THAN A
HEAVY SHOWER. IRRESPECTIVE OF CONVECTION... BACKGROUND WINDS OF 15-
20 MPH WITH FREQUENT GUSTS TO 25-30 MPH ARE LIKELY.

TEMPERATURES: WARM AND HUMID TODAY WITH HIGHS FROM THE MID 60S NW TO
THE MID 70S EAST. LOWS TONIGHT FROM THE MID 40S NW... WITH THE FRONT
PASSING EAST OF THIS AREA OVERNIGHT... RANGING TO AROUND 60 IN THE
FAR EAST WHERE OCCASIONAL SHOWERS WILL HOLD OVERNIGHT. -GIH

&&

.SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
AS OF 330 AM WEDNESDAY...

THE MAIN CHANGE TO THIS FORECAST PERIOD WILL BE TO HOLD ONTO BOTH
CLOUDINESS AND THE RAIN CHANCES LONGER... ESPECIALLY OVER THE
EASTERN CWA. THE COLD FRONT IS EXPECTED TO SHIFT SLOWLY EAST OF
HIGHWAY 1 THURSDAY... EASING TO COASTAL SECTIONS BY THURSDAY
EVENING. THE MID LEVEL TROUGH AXIS WILL HOLD WELL TO OUR WEST
HOWEVER... FROM THE GREAT LAKES TO THE GULF STATES WITH A FAIRLY
SLOW EASTWARD PUSH THU NIGHT... AND THE RESULTING SOUTHWESTERLY
STEERING FLOW PARALLEL TO THE FRONTAL ZONE WILL HINDER THE FRONT`S
EASTWARD PUSH. MUCH ABOVE NORMAL PW VALUES WILL CONTINUE TO STREAM
OVER ERN NC THU/THU NIGHT WITH MULTIPLE WEAK LOW PRESSURE CENTERS
TRACKING ALONG THE FRONT OVER COASTAL NC... SO EXPECT A GOOD CHANCE
OF RAIN TO HOLD OVER THE ERN CWA INTO THU NIGHT... WHEN A POTENT MID
LEVEL VORTICITY MAX EJECTS OUT OF THE TROUGH BASE AND CROSSES THE
CAROLINAS THU NIGHT... FINALLY SHOVING THE SURFACE FRONTAL ZONE
OFFSHORE. EXPECT HIGHS IN THE 50S TO NEAR 60 THU... WITH CLOUDY
SKIES AREAWIDE... GIVING WAY IN THE NW TO PARTIAL CLEARING LATE.
LOWS THU NIGHT FROM THE LOWER TO UPPER 30S... ALTHOUGH THE NEAR- OR
SUB-FREEZING AIR WILL BE CHASING THE PRECIP... AND NO WINTRY WEATHER
IS EXPECTED. -GIH

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
AS OF 310 AM WEDNESDAY...

FRIDAY AND SATURDAY: THE FRONT AND ALL ASSOCIATED PRECIPITATION WILL
FINALLY EXIT TO THE EAST ON FRIDAY MORNING. IN ITS WAKE...HIGH
PRESSURE WILL FORM OVER THE DEEP SOUTH AND DRY THINGS OUT THROUGH
SATURDAY. TEMPERATURES WILL BE COOL...BUT ONLY A FEW DEGREES BELOW
NORMAL FOR THIS TIME OF YEAR...AROUND 50 DEGREES FOR DAYTIME HIGHS
AND LOWS IN THE UPPER 20S TO LOWER 30S.

SUNDAY THROUGH TUESDAY: THE FORECAST STARTS TO BECOME A LOT MORE
UNCERTAIN ON SUNDAY AND THIS LACK OF CONFIDENCE PERMEATES THROUGH
THE END OF THE FORECAST PERIOD. LOOKING AT THE VERY BIG PICTURE...AS
A PREFACE...THE ARCTIC OSCILLATION IS FORECASTED TO START TURNING
NEGATIVE ABOUT THIS TIME...INDICATING A HIGHER POSSIBILITY FOR
COLDER TEMPERATURES AND POTENTIALLY WINTER WEATHER.

AT THE SAME TIME...A VERY DEEP UPPER LEVEL TROUGH WILL DIG DOWN OVER
THE MISSISSIPPI VALLEY AND IS PROGGED TO FORM A CUTOFF LOW OVER THE
TENNESSEE VALLEY AND PUSH EASTWARD. AT THE SAME TIME...A STRONG
SURFACE LOW WILL BEGIN TO FORM OFF OF THE SOUTHEAST COAST AND TRACK
NORTHEASTWARD. THE AMOUNT OF INTERACTION BETWEEN THESE TWO FEATURES
WILL LIKELY DETERMINE IF WE HAVE ANY PRECIPITATION ON SUNDAY OR NOT.
THE EUROPEAN SOLUTION HAS BEEN THE FAVORED SOLUTION FOR THIS SYSTEM
WHICH KEEPS PRECIPITATION TO OUR EAST BUT THE GFS HAS COME MORE IN
LINE OVER THE PAST COUPLE OF RUNS. THE PROBLEM WITH IT AT THIS TIME
IS THAT IT IS PRODUCING A VERY STRONG UPPER LOW WHICH LOOKS
ANOMALOUSLY DEEP AT THIS POINT. THIS STRONG UPPER LOW WRAPS
PRECIPITATION BACK ACROSS OUR CWA. AFTER CHECKING THIS SCENARIO
AGAINST THE ECMWF ENSEMBLE MEMBERS...VERY FEW HAVE THIS HAPPENING
BUT THERE ARE A COUPLE OF MEMBERS THAT DEPICT SOMETHING
SIMILAR...ENOUGH CAUSE FOR REASONABLE DOUBT. LOOKING AT FORECAST
SOUNDINGS...IF THIS OUTLIER SCENARIO WERE TO COME TO
FRUITION...THICKNESS VALUES IN THE NOMOGRAM ARE RIGHT ON THE BORDER
BETWEEN SNOW...RAIN OR SNOW...AND INDETERMINATE. THIS MEANS THAT AT
THIS POINT...THERE IS VERY LOW CONFIDENCE ON WHETHER OR NOT THIS
SYSTEM COULD PRODUCE SOME WINTER P-TYPES ACROSS OUR AREA ON SUNDAY.

WITH ALL THAT BEING SAID...THE MOST LIKELY PLACES THAT SEE
PRECIPITATION WILL BE IN THE EAST...WHERE THICKNESSES WILL MOST
LIKELY BE HIGH ENOUGH TO AVOID THE WINTER P-TYPES. THEREFORE HAVE
INCLUDED ONLY SLIGHT CHANCE OF RAIN IN THE SOUTHEAST AT THIS TIME IN
THE FORECAST WITH THE ASTERISK OF CLOSELY MONITORING FUTURE MODEL
RUNS.

AFTER A SHORT BREAK ON MONDAY...A SECOND VERY STRONG UPPER TROUGH
BRINGS ARCTIC AIR OUT OF CANADA AND A LOW PRESSURE SYSTEM DEVELOPS
OVER THE GREAT LAKES. AS THIS DIVES SOUTH...THE POTENTIAL FOR
ANOTHER COASTAL LOW EXISTS FOR TUESDAY BUT MODELS ARE VERY FUZZY ON
DETAILS BECAUSE ALL OF THIS DEPENDS ON THE EVOLUTION OF THE FIRST
TROUGH AND SYSTEM. THEREFORE HAVE KEPT THE FORECAST DRY AT THIS TIME
FOR TUESDAY UNTIL MORE DETAILS EMERGE. WITH THICKNESSES PLUNGING
EVEN FURTHER...P-TYPE ISSUES COULD POTENTIALLY BECOME A PROBLEM FOR
THE MIDDLE OF NEXT WEEK. STAY TUNED.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
AS OF 650 AM WEDNESDAY...

POOR AVIATION CONDITIONS WILL DOMINATE OVER THE NEXT 24 HOURS...
WITH A PERIOD OF LOW LEVEL WIND SHEAR LIKELY ESPECIALLY AT
INT/GSO/RDU THROUGH 16Z-18Z. CONDITIONS ARE CURRENTLY LIFR AT ALL
TAF SITES EXCEPT RWI. A WARM FRONT LOCATED NEAR THE NC/SC STATE LINE
WILL SURGE NORTHWARD THROUGH THE AREA THIS MORNING... RESULTING IN
THE INITIALLY FAIRLY LIGHT SURFACE WINDS FROM THE SE VEERING TO
SOUTHERLY AND INCREASING THIS MORNING BETWEEN 12Z AND 15Z. AFTER 15Z
THIS MORNING... THE IFR/LIFR CIGS WILL START TO LIFT AND MIX OUT TO
MVFR/VFR BRIEFLY BEFORE THE ARRIVAL OF WIDESPREAD SHOWERS AND
ISOLATED STORMS FROM THE WEST. CONDITIONS WILL QUICKLY DROP BACK TO
MVFR OR IFR FROM WEST TO EAST AS THE SHOWERS/STORMS ASSOCIATED WITH
A COLD FRONT CROSSES THE AREA. WINDS WILL BE STRONG AND GUSTY TODAY
THROUGH THIS EVENING... SUSTAINED AT 12-18 KTS WITH GUSTS UP TO 20-
30 KTS... AND THESE GUSTS WILL BE STRONGER IN AND NEAR HEAVY SHOWERS
AND EMBEDDED STORMS THIS AFTERNOON. AN IMPROVEMENT BACK TO VFR IS
EXPECTED AFTER THE COLD FRONT PASSAGE FROM LATE EVENING THROUGH THE
OVERNIGHT... WHEN WINDS WILL SHIFT AROUND TO NORTHWEST THEN NORTH.
THE LLWS THREAT WILL BE GREATEST AT INT/GSO/RDU AFTER 09Z THIS
MORNING AS A 50-60 KT SOUTHERLY LOW LEVEL JET ARRIVES FROM THE WEST.
THE LLWS THREAT WILL LARGELY END AROUND 17Z-18Z AS THE JET WEAKENS
AND SHIFTS TO OUR OUR EAST.

LOOKING BEYOND 12Z THU MORNING... RAIN CHANCES WILL LINGER THROUGH
THU AT RWI/FAY AS THE FRONT VERY SLOWLY SHIFTS EAST OF THE COAST...
AND FAY/RWI AND PERHAPS RDU WILL LIKELY SEE A RETURN TO AREAS OF
RAIN AND MVFR CONDITIONS THU INTO THU NIGHT AS AN UPPER LEVEL
DISTURBANCE CROSSES THE REGION. VFR CONDITIONS ARE LIKELY FRI
THROUGH SAT AS HIGH PRESSURE BUILDS INTO AND OVER THE AREA FROM THE
WEST. LOW PRESSURE TRACKING JUST OFF THE SOUTHEAST COAST ON SUNDAY
MAY BRING A CHANCE OF SUB-VFR CONDITIONS AND BRISK WINDS AT RWI/FAY
RDU TO END THE WEEKEND. -GIH

&&

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

&&

$$

SYNOPSIS...HARTFIELD
NEAR TERM...HARTFIELD
SHORT TERM...HARTFIELD
LONG TERM...ELLIS
AVIATION...HARTFIELD


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