Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS62 KRAH 301041
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
640 AM EDT TUE SEP 30 2014

.SYNOPSIS...WEAK LOW PRESSURE OVER NORTHEAST FLORIDA WILL TRACK
NORTHEASTWARD OFF THE SOUTHEAST COAST TODAY. WEAK HIGH PRESSURE WILL
BUILD OVER THE AREA FROM THE NORTH WEDNESDAY THROUGH THURSDAY. A
STRONG STORM SYSTEM WILL APPROACH FROM THE WEST ON FRIDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 330 AM TUESDAY...

UPDATE: FOG HAS BECOME QUITE DENSE OVER MOST OF CENTRAL NC (WITH THE
EXCEPTION OF THE FAR SOUTHEAST SECTIONS)... WARRANTING ISSUANCE OF A
DENSE FOG ADVISORY UNTIL 10 AM. VSBYS SHOULD GRADUALLY IMPROVE
DURING THE 9AM-11AM TIME FRAME.

EARLIER DISCUSSION FROM 222 AM TUESDAY...

TODAY... FIRST CONCERN EARLY THIS MORNING IS THE DEGREE OF FOG
DEVELOPMENT OVER THE AREA THUS FAR. THE MID LEVEL SHORTWAVE TROUGH
IS NOW HEADING EAST OFF THE CAROLINA COAST... WITH THE VEIL OF
MID/HIGH CLOUDS DEPARTING ALONG WITH IT. THE DAMP GROUND COMBINED
WITH THE CLEARING SKIES AND LIGHT/CALM WINDS SHOULD CONTINUE TO
FOSTER DEVELOPMENT OF LOW CLOUDS AND FOG EARLY THIS MORNING...
ALTHOUGH THE CURRENT PATCHY/FLEETING NATURE OF THESE CONDITIONS
(SEVERAL SITES HAVE BOUNCED AROUND BETWEEN 1/4 MI AND 5 MI IN FOG
THE LAST FEW HRS) GIVES US PAUSE AS TO THE NEED FOR A DENSE FOG
ADVISORY. THE HRRR DEPICTS A FAIRLY SOLID DECK OF LOW CLOUDS/FOG
FORMING OVER THE NEXT FEW HOURS HOWEVER. WILL CONTINUE TO MONITOR
THE OBSERVED TRENDS. IF VSBYS DO DROP AND HOLD THERE FOR OVER AN
HOUR... THEY`RE LIKELY TO HOLD FIRM THROUGH MID MORNING... GIVEN THE
WEAK WIND FIELD THROUGH THE LOWEST FEW THOUSAND FEET RESULTING IN
MINIMAL STIRRING/DISPERSION HORIZONTALLY OR VERTICALLY. WILL KEEP
SKIES PARTLY TO MOSTLY CLOUDY THROUGH MID MORNING TO ACCOUNT FOR
THIS. THEN... ONCE HEATING AND SUBSEQUENT MIXING HELPS TO DISPERSE
THE FOG/STRATUS... EXPECT A GOOD BIT OF SUNSHINE THROUGH THE DAY...
WITH FLAT AFTERNOON STRATOCU LIKELY TO STAY SCATTERED AT WORST. WITH
THICKNESSES CLOSE TO SEASONAL NORMALS... STILL LOOK FOR HIGHS WITHIN
A FEW DEGREES OF 80.

FOR TONIGHT: THE SURFACE LOW TRACKING TOWARD THE NE WELL OFF THE SE
COAST WILL BE FAR ENOUGH TO OUR SE TO MINIMIZE ANY IMPACT ON CENTRAL
NC. THE WEAK LOW LEVEL FLOW PATTERN HOLDS WITH A WEAK HIGH PRESSURE
RIDGE SPANNING THE AREA AND A VERY WEAK SURFACE LOW/INVERTED TROUGH
OVER PA/WV/VA... A REFLECTION OF THE CLIPPER MID LEVEL VORTEX NOW
OVER ERN MI THAT IS EXPECTED TO CROSS THE MIDATLANTIC REGION REGION
LATE TONIGHT THROUGH WED MORNING. MODELS VARY IN THEIR IMPACTS ON
OUR WEATHER WITH THIS FEATURE... WITH THE NAM MUCH MORE BULLISH THAN
THE GFS IN TAKING A SLUG OF 850-700 MB MOISTURE EAST ACROSS THE AREA
TONIGHT. THIS SEEMS A BIT OVERDONE BUT IT IS SOMEWHAT SUPPORTED BY
OBSERVED SOUNDINGS UPSTREAM... SO WILL RETAIN A FEW CLOUDS OVER THE
AREA OVERNIGHT... AND LATER FORECASTS CAN INCREASE THIS COVERAGE IF
LATER GUIDANCE SUPPORTS THE NAM. LOWS 57-60. -GIH

&&

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 245 AM TUESDAY...

AS NOTED ABOVE... WE SHOULD SEE AT LEAST SOME SCATTERED CLOUDS
MAINLY OVER THE EAST WED MORNING. THE PRESENCE OR LACK OF SUCH
CLOUDS WILL IMPACT HOW MUCH FOG FORMS WED MORNING. WE SHOULD SEE AT
LEAST SOME LIGHT FOG TO START THE DAY... AND PERHAPS MORE DENSE IF
THE AFOREMENTIONED CLIPPER-ASSOCIATED CLOUDS DO NOT HAPPEN.
OTHERWISE... EXPECT A PARTLY TO MOSTLY SUNNY DAY. THE CLIPPER LOW
WILL CROSS NEW ENGLAND AS THE STRONG VORTICITY MAX ROUNDS ITS
BASE... SHIFTING OFF THE NJ COAST... AND WE SHOULD SEE A BIT MORE
FLAT DAYTIME CUMULUS FROM THE TRIANGLE NORTH AND EAST CLOSER TO THE
LOW. MODELS SHOW WEAK MID LEVEL RIDGING PUSHING IN FROM THE WEST
LATE... BETWEEN THE DEPARTING CLIPPER AND A DEEPENING TROUGH
COVERING THE EASTERN ROCKIES AND HIGH PLAINS LATE WED/WED NIGHT.
WHILE MODELS SHOW A MINOR PERTURBATION TRACKING EASTWARD OVER THE
SOUTHEAST STATES WED NIGHT... THIS SHOULD BE OF LITTLE CONSEQUENCE
WITH DEEP DRY AIR MOVING IN. EXPECT DRY WEATHER THROUGH WED NIGHT.
THICKNESSES ARE EXPECTED TO START WED ABOUT 10 M ABOVE NORMAL...
SUPPORTING HIGHS ABOUT A CATEGORY ABOVE NORMAL... 80-84. SOME
CLOUDINESS POSSIBLE WED NIGHT ESPECIALLY OVER THE WEST WHERE MODELS
INDICATE AN UPTICK IN LOW LEVEL MOISTURE TRANSPORT GENERATED BY
LIGHT BUT CONFLUENT AND UPSLOPE-DIRECTED LOW LEVEL FLOW. LOWS WITHIN
A COUPLE DEGREES OF 60. -GIH

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
AS OF 300 AM TUESDAY...

FOR THE PERIOD THURSDAY THROUGH THURSDAY NIGHT...A MID-LEVEL RIDGE
AXIS BUILDS INTO CENTRAL NORTH CAROLINA THURSDAY...WITH THE AXIS
MOVING EAST THURSDAY NIGHT. THE GUIDANCE HAS CONTINUED TO FORECAST
VERY MINOR QPF IN CENTRAL NORTH CAROLINA DURING THIS PERIOD...WITH
THE GFS FORECASTING THIS THURSDAY AND THE NAM MORE THURSDAY NIGHT.
THE GFS DOES HAVE A RELATIVE MAXIMUM OF 850MB THETA-E AIR OVER
CENTRAL NORTH CAROLINA THURSDAY WITH WEAK 850MB LIFT...BUT HEIGHTS
ALOFT ARE RISING AND ANY LOW-LEVEL FORCING WITH ANY SURFACE BOUNDARY
SHOULD BE WEAK. LIFTED INDICES ARE ABOVE 0C...AND MLCAPE IN THE
LOWEST KM DOES NOT REGISTER AS BUFR SOUNDINGS FROM BOTH THE NAM AND
GFS APPEAR CAPPED. GIVEN THE ORIENTATION OF 1000-500MB
THICKNESSES...POSSIBLY A SHOWER COULD DRIFT SOUTHEAST FOLLOWING THE
THERMAL WIND FROM HIGHER TERRAIN AND GET CLOSE TO THE NORTHWEST
PIEDMONT THURSDAY AFTERNOON OR EVENING...BUT GIVEN THE UNCERTAINTY
WILL KEEP THE FORECAST DRY. MOS GUIDANCE POPS ARE IN SINGLE FIGURES
IN BOTH THE MAV AND THE MET. WITH AT LEAST A PARTLY SUNNY SKY
EXPECTED...1000-850MB THICKNESSES WOULD SUGGEST LOWER TO MID 80S FOR
HIGHS...IN CONJUNCTION WITH MAV AND MET MOS GUIDANCE. OVERNIGHT LOWS
THURSDAY NIGHT NEAR 60 IN THE NORTHEAST PIEDMONT AND NORTHERN
COASTAL PLAIN UNDERNEATH THE RIDGE AXIS ALOFT FOR A GOOD PART OF THE
NIGHT...LOWER 60S ELSEWHERE AND POSSIBLY ON THE HIGHER END OF THE
LOWER 60S TOWARD THE TRIAD AS THE WINDS OFF OF THE SURFACE START TO
INCREASE OVERNIGHT.

FOR THE PERIOD FRIDAY THROUGH TUESDAY...THE ECMWF AND THE GFS
CONTINUE TO BE IN FAIRLY GOOD AGREEMENT WITH THE TIMING OF AN
ELONGATED MID-LEVEL SHORTWAVE MOVING INTO CENTRAL NORTH CAROLINA BY
00Z SATURDAY AND THEN EAST OF THE AREA BY 12Z SATURDAY. ONE TREND
HAS BEEN FOR THE MID-LEVEL RIDGE TO BE SLIGHTLY MORE AMPLIFIED...
WHICH...IF THE TREND CONTINUES...COULD SLOW THE ONSET OF ANY SHOWERS
OR THUNDERSTORMS DURING THE DAY FRIDAY. LAPSE RATES ON COARSE GFS
AND ECMWF MODEL SOUNDINGS ARE NEAR MOIST ADIABATIC AT BEST...SO
INSTABILITY SHOULD BE LIMITED. STILL...WITH WINDS OFF OF THE SURFACE
INCREASING TO AT OR A LITTLE ABOVE 30KT AHEAD OF THE COLD FRONT...
CURRENT THINKING IS THAT ANY STRONGER STORM COULD HAVE A GUSTY
WIND...THOUGH NOT CONFIDENT CURENTLY IN THE PROBABILITY OF ISOLATED
SEVERE WEATHER GIVEN THE MARGINAL LAPSE RATES. DRY CONDITIONS WILL
BE FORECAST SATURDAY THROUGH SUNDAY...THOUGH THE ECMWF DOES CONTINUE
TO FORECAST GREATER DIGGING WITH UPPER-LEVEL LOW PRESSURE MOVING
THROUGH THE OHIO VALLEY AND EAST ACROSS AREAS JUST NORTH OF CENTRAL
NORTH CAROLINA SATURDAY NIGHT. AGAIN...THE TREND OF THIS WILL NEED
TO BE WATCHED...BUT CURRENTLY THE MID-LEVEL MOISTURE ASSOCIATED WITH
THE UPPER LOW ON THE ECMWF STAYS NORTH OF CENTRAL NORTH CAROLINA
SATURDAY NIGHT INTO EARLY SUNDAY. BEHIND THE COLD FRONT ON SATURDAY
OR SATURDAY NIGHT...HOWEVER...SOME JET STREAK CIRRUS COULD OCCUR IF
THE GFS AND ECMWF UPPER-LEVEL MOISTURE FORECASTS VERIFY IN
CONJUNCTION WITH THE JET AXIS ALOFT.

THE ECMWF IS ALSO MORE AMPLIFIED WITH ANOTHER IN A SERIES OF MID-
LEVEL WAVES IN THE NORTHWEST FLOW...THIS ONE APPROACHING THE
SOUTHERN APPALACHIANS MONDAY. THE GFS IS DRY WITH LITTLE FORCING...
WHILE THE ECMWF HAS MORE OF A SURFACE REFLECTION WITH THE MID-LEVEL
WAVE AND ENOUGH MID-LEVEL MOISTURE FOR LIGHT PRECIPITATION OVER THE
WESTERN AND NORTHWEST PIEDMONT LATE MONDAY AFTERNOON OR MONDAY
NIGHT. WITH SURFACE HIGH PRESSURE OVER THE GULF...IF THERE IS ANY
PRECIPITATION MONDAY...THE THOUGHT IS IT WOULD BE MID-LEVEL DRIVEN
AND MOSTLY LIGHT. FOR THIS FORECAST WILL TREND A LITTLE MORE
PESSIMISTIC ON THE LAST DAY OF THE LONG-TERM PERIOD...INCREASING
CLOUDS BUT KEEPING THE OVERALL FORECAST DRY.

AFTER HIGHS IN THE MID 70S TO NEAR 80 FRIDAY AHEAD OF THE FRONT...
BY SATURDAY NIGHT...AS THE GUIDANCE STILL SHOWS CHILLY 1000-850MB
THICKNESSES INTO THE 1340S...THERE SHOULD BE AT LEAST A FEW 40S OVER
THE WESTERN AND NORTHERN PIEDMONT. MODEST WARMING FOR THE END OF THE
WEEKEND AND THE START OF NEXT WEEK. HIGHS SHOULD BE BACK AT LEAST IN
THE LOWER TO MID 70S FOR MONDAY.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
AS OF 640 AM TUESDAY...

ADVERSE AVIATION CONDITIONS ARE LIKELY TO HOLD OVER CENTRAL NC
THROUGH 14Z OR 15Z THIS MORNING... WITH IMPROVEMENT TO VFR TO FOLLOW
BY LATE MORNING... WHICH WILL HOLD THROUGH 04Z (MIDNIGHT TONIGHT).
THE MID LEVEL TROUGH AXIS OVER THE ERN CAROLINAS WILL CONTINUE TO
SHIFT EAST AND OFFSHORE THIS MORNING. THE RESULTANT CLEARING SKIES
AND LIGHT WINDS HAVE LED TO LOW STRATUS/FOG DEVELOPMENT THIS
MORNING. THESE IFR/LIFR CONDITIONS HAVE BEEN DISCONTINUOUS... WITH
AVIATION CONDITIONS PERIODICALLY SWINGING WILDLY BETWEEN LIFR AND
MVFR... MAKING THE TAFS CHALLENGING THIS MORNING. PILOTS SHOULD BE
PARTICULARLY ALERT FOR POSSIBLE VFR HOLES WITHIN IFR/LIFR CONDITIONS
THROUGH MID MORNING. OTHERWISE... ANY CIGS SHOULD LIFT AND BEGIN TO
BREAK UP BY 15Z OR 16Z... WITH VFR CONDITIONS THEN PREVAILING
THROUGH THE AFTERNOON AND EVENING HOURS. AFTER MIDNIGHT... WE EXPECT
REDEVELOPMENT OF SHALLOW IFR OR LIFR FOG LATE IN THE TAF VALID
PERIOD... WITH THE WORST CONDITIONS EXPECTED BETWEEN 08Z AND 12Z.
SURFACE WINDS WILL REMAIN LIGHT/VARIABLE (MAINLY FROM THE NORTHWEST)
MOSTLY UNDER 5 KTS TODAY/TONIGHT.

LOOKING BEYOND 12Z WED MORNING... SUB-VFR FOG EARLY WED MORNING
SHOULD MIX OUT BY 15Z. OTHERWISE... VFR CONDITIONS WILL PREVAIL
THROUGH FRI... ALTHOUGH SHALLOW IFR GROUND FOG IS AGAIN POSSIBLE
AREAWIDE 08Z-13Z EACH MORNING THU AND FRI. A STRONG FRONTAL SYSTEM
WILL BRING A GOOD CHANCE OF SUB-VFR CONDITIONS WITHIN WIDESPREAD
SHOWERS/STORMS FRI AFTERNOON INTO FRI NIGHT. HIGH PRESSURE WILL THEN
BUILD IN YIELDING VFR CONDITIONS SAT. -GIH

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY UNTIL 10 AM EDT THIS MORNING FOR
NCZ007>011-021>028-038>043-073>077-083>086-088.

&&

$$

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


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.