Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 070743
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
340 AM EDT TUE JUL 7 2015

.SYNOPSIS... AN UPPER TROUGH ACROSS THE SOUTHERN APPALACHIANS WILL
LIFT AWAY FROM THE REGION TODAY. A RIDGE OF HIGH PRESSURE WILL THEN
DEVELOP OVER THE SOUTHEAST AND STRENGTHEN THROUGH THE REMAINDER OF
THE WORK WEEK.

&&

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

WATER VAPOR IMAGERY SHOWS A LING SHEAR AXIS PARALLEL IN APPALACHIAN
SPINE THIS MORNING...WITH THE FORMER UPPER LOW OVER WESTER VIRGINIA
AS IT CONTINUES TO SHEAR AND LIFT TO THE NORTHEAST.  AT THE
SURFACE...A TROUGH EXTENDS DOWN THE PIEDMONT OF VA AND NC...WITH A
STRONGER SYNOPTIC FRONT WELL TO OUR NORTHWEST MOVING ACROSS WI/IL/MO.

TODAY...EARLY MORNING STRATUS IS POSSIBLE ACROSS THE COASTAL PLAIN
WHERE SOUTHWESTERLY 925MB FLOW IS AROUND 15-20KT...BUT THE RAP/HRRR
SHOWS LITTLE IN THE WAY OF SATURATION...SO ANYTHING THAT FORMS WILL
BE VERY THIN AND WILL BURN OFF QUICKLY.   THE AFOREMENTIONED SHEAR
AXIS WILL SHIFT EAST ACROSS THE AREA TODAY..BUT SOME WESTERLY MID-
LEVEL FLOW WILL CONTINUE TO ADVECT DRIER AIR IN FROM THE WEST...WITH
PW FALLING BELOW 1.5" ACROSS THE WESTERN HALF OF THE CWA AND
DEWPOINTS LIKELY TO MIX OUT INTO THE LOW/MID 60S AGAIN CROSS THE
WEST. ANY APPRECIABLE MLCAPE WILL BE CONFINED TO THE COASTAL
PLAIN..AND EVEN THERE VALUES SHOULD BE AROUND 1000 J/KG OR LESS.
THUS...THE FORCING/INSTABILITY OVERLAP REALLY APPEARS TO BE NEAR I-
95 AND EAST THIS AFTERNOON...SO POPS HAVE BEEN LOWERED AND FOCUSED
ACROSS THE EAST....AND THIS IS GENERALLY SUPPORTED BY THE HRR AND
VARIOUS OTHER CAMS.

HIGHS SHOULD BE AS MUCH AS 2-4 DEGREES WARMER TODAY AS THICKNESSES
WILL BE 10-15M HIGHER AND MIXING DEEP. THE PREVIOUS FORECAST
REFLECTS THIS WARMING AND WILL BE CONTINUED.

CONVECTION SHOULD BE DIURNALLY DRIVEN TODAY AND COME TO AN END BY
00Z...WITH LOWS DROPPING INTO THE UPPER 60S AND LOWER 70S UNDER
CLEARING SKIES BUT AN UNCHANGED AIRMASS.

&&

.SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
AS OF 340 AM TUESDAY...

THE SUBTROPICAL RIDGE AND BERMUDA HIGH WILL CONTINUE TO BUILD ACROSS
THE SOUTHEAST ON WEDNESDAY...WITH A SHORTWAVE CROSSING THE GREAT
LAKES REGION EARLY WEDNESDAY AND THE ATTENDANT COLD FRONT BECOMING
LAID OUT WEST TO EAST FROM THE MIDWEST TO THE MID-ATLANTIC STATES.
THE LEE TROUGH WILL AGAIN SET UP OVER THE NC PIEDMONT...WITH WEAK
INSTABILITY AGAIN FOCUSED ACROSS THE EASTERN HALF OF THE CWA.  ANY
CONVECTION SHOULD PRIMARILY BE CONFINED TO THE SEABREEZE AND/OR
HIGHER TERRAIN CIRCULATIONS.   THE BIG UNCERTAINTY REGARDING
CONVECTION IS WHETHER OR NOT AN UPPER DISTURBANCE...ONE OF A SERIES
OF DISTURBANCES TO TRACK NEAR THE FRONTAL ZONE TO OUR NORTH...WILL
ENHANCE CONVECTION ALONG BLUE RIDGE...WHICH COULD CONCEIVABLY GROW
UPSCALE INTO A LINE OF STORMS THAT MOVES INTO THE PIEDMONT DURING
THE LATE AFTERNOON AND EVENING GIVEN THE DEEP MIXING AND STEEP LOW-
LEVEL LAPSE RATES (WHICH COULD PROMOTE THE MERGING OF STRONG
OUTFLOWS).  RIGHT NOW THIS SEEMS MORE LIKELY TO OUR NORTH...BUT GIVEN
THE POSSIBILITY...WILL KEEP A SLIGHT CHANCE POP ACROSS THE NORTH
INTO THE EVENING HOURS.  HIGHS WILL AGAIN BE IN THE LOW TO MID
90S...MAYBE A DEGREE WARMER BASED ON THICKNESSES.  LOWS WEDNESDAY
NIGHT IN THE LOWER 70S.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
AS OF 325 AM TUESDAY...

THU: THE WEAK PIEDMONT SURFACE TROUGH WILL HOLD OVER CENTRAL NC...
WHILE THE SYNOPTIC FRONTAL ZONE SETTLES SOUTHWARD INTO VA. EXPANSIVE
MID LEVEL RIDGING FROM THE LOWER MISS VALLEY ACROSS THE SOUTHEAST
STATES CONTINUES TO SLOWLY RETROGRADE WHILE SUPPRESSING THE
WESTERLIES TO OUR NORTH. ABUNDANT HEATING IS ASSURED.... WHICH WILL
PUSH THICKNESSES UP TO 5-10 M ABOVE NORMAL... INDICATING HIGHS IN
THE LOWER-MID 90S. FALLING DEWPOINTS WITH MIXING BY AFTERNOON SHOULD
KEEP HEAT INDICES BELOW CRITICAL VALUES OVER MUCH OF THE CWA
(ALTHOUGH THEY MAY EXCEED 100F BRIEFLY IN THE SE CWA). GIVEN THE
DEEP LAYER SUBSIDENCE AND NEAR-NORMAL PW... ANY SUBSTANTIAL RAIN
CHANCES WILL BE VERY LOW AND CONFINED TO THE EXTREME NORTH...
POTENTIALLY ALONG OUTFLOW EMANATING FROM CONVECTION ALONG THE FRONT
(PERHAPS ENHANCED BY A LOW CROSSING MD/DE)... AND ALONG AN INLAND-
MOVING SEA BREEZE LATE IN THE DAY.

FRI: THE SYNOPTIC FRONT TO THE NORTH APPEARS LIKELY TO DIP NEAR OR
JUST INTO NE NC... WITH A RESIDUAL OUTFLOW POTENTIALLY DROPPING
FURTHER SOUTH WELL INTO NORTH CENTRAL NC... WHILE ALOFT... THE MID
LEVEL ANTICYCLONE CENTER CONTINUES TO DRIFT WESTWARD OVER THE LOWER
MISS VALLEY. WITH THE SUBSEQUENT TILT/DIP IN THE WESTERLIES DOWN THE
MIDATLANTIC COAST... MODELS DO TREND TOWARD A BIT MORE WEAK
SHORTWAVE ENERGY TRACKING SOUTHEASTWARD BRUSHING NE NC FRI NIGHT...
ALTHOUGH THE PROJECTED INSTABILITY SHOULD BE LOW (MUCAPE UNDER 750
J/KG ON THE GFS)... AND PW WILL ONLY BE SLIGHTLY ELEVATED OVER THE
ERN CWA. WILL PLACE LOW CHANCE POPS ACROSS THE NORTH/NE CWA AND IN
THE COASTAL PLAIN... ALONG THE WEAK SURFACE TROUGH. THICKNESSES WILL
AGAIN BE 5-10 M ABOVE NORMAL... SO EXPECT HIGHS ONCE AGAIN IN THE
LOW-MID 80S. LOWS 70-74 WITH LINGERING ISOLATED POPS OVER THE FAR
NORTH AND NORTHEAST OVERNIGHT.

SAT-MON: THE COMBINATION OF THE BUILDING RIDGE OVER THE SRN PLAINS
AND UP THE FRONT RANGE OF THE ROCKIES AND RESULTING STRENGTHENING NW
FLOW FROM THE UPPER MIDWEST THROUGH THE LOWER GREAT LAKES TO THE
MIDATLANTIC COAST WILL PLACE NC IN A MORE ACTIVE AND VOLATILE
WEATHER PATTERN... HIGHLIGHTED BY POCKETS OF MID LEVEL SHORTWAVE
ENERGY CROSSING OUR REGION IN NW STEERING FLOW... TRACKING ALONG THE
OLD DIFFUSE SURFACE FRONTAL ZONE. NORTHERN AND EASTERN PORTIONS OF
THE FORECAST AREA SHOULD SEE THE BEST CHANCES FOR CONVECTION...
ORIGINATING IN A HIGHLY UNSTABLE ENVIRONMENT OVER THE MIDWEST AND
THE OH VALLEY MOVING SOUTHEASTWARD OVER VA/NC. WHILE WE CAN`T
ACCURATELY TRACK SPECIFIC FEATURES AT THIS RANGE... THE IMPROVING
SHEAR AND INSTABILITY ALONG WITH GREATER DYNAMIC FORCING FOR ASCENT
SUPPORT BOOSTING POPS TO SLIGHTLY ABOVE CLIMATOLOGY DURING THIS
PERIOD... AND NOT NECESSARILY PEAKING IN THE TYPICAL LATE-DAY TIME
FRAME EITHER... AS HIGH LAPSE RATES WITHIN AN UPSTREAM EML MAY
SUSTAIN NOCTURNAL CONVECTION AS IT MOVES SOUTHEAST. STILL EXPECT
ABOVE NORMAL THICKNESSES TO EQUATE TO WARM TEMPS TOPPING OUT DAILY
IN THE LOWER TO MID 90S... AND THE THREAT OF 100+F HEAT INDEX VALUES
PARTICULARLY FROM THE TRIANGLE TO THE SOUTH AND EAST WILL LINGER
INTO EARLY NEXT WEEK. -GIH

&&

.AVIATION /00Z TUESDAY THROUGH FRIDAY/...
AS OF 140 AM TUESDAY...

VFR CONDITIONS FOR MOST OF THE REMAINDER OF THE NIGHT...ALTHOUGH A
LITTLE STRONGER FLOW JUST ABOVE THE SURFACE OVER THE COASTAL PLAIN
MAY LEAD TO SOME STRATUS BY 10-12Z.  HOWEVER...MODEL GUIDANCE ISN`T
REALLY INDICATING MUCH MORE THAN JUST A  FEW PATCHES OF IFR
STRATUS...SO THE LATEST TAF WILL REFLECT LESS IN THE WAY OF
RESTRICTIONS.  WHATEVER LOW CLOUDS THAT DO FORM WILL BURN OFF BY
14Z...AND SCATTERED CU IN THE 3-4K FT RANGE WILL DEVELOP FOR THE
AFTERNOON HOURS.  WITH DRIER AIR ON CENTRAL NC...ONLY WIDELY
SCATTERED SHOWERS AND ISOLATED STORMS ARE EXPECTED OVER THE COASTAL
PLAIN...PRIMARILY IN THE VICINITY OF KFAY AND/OR KRWI AFTER 18Z.

OUTLOOK...MOSTLY VFR CONDITIONS THROUGH THE END OF THE WEEK AS HIGH
PRESSURE DOMINATES THE REGION.  SOME AFTERNOON STORMS ARE POSSIBLE
EACH DAY...ALONG WITH EARLY MORNING VSBY RESTRICTIONS.

&&

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

&&

$$

SYNOPSIS...BLAES
NEAR TERM...22
SHORT TERM...22
LONG TERM...HARTFIELD
AVIATION...22


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