-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 170725
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
315 AM EDT MON JUN 17 2013

.SYNOPSIS...
A COLD FRONT WILL APPROACH FROM THE NORTHWEST TODAY AND ACROSS OUR
REGION LATE TUESDAY.

&&

.NEAR TERM /THROUGH MONDAY NIGHT/...
-- Changed Discussion --
AS OF 315 AM MONDAY...

HIGH CLOUDINESS HAS BEEN INCREASING AND PATCHY LIGHT RAIN HAS BEEN
THREATENING TO ENCIRCLE THE RAH CWFA OVERNIGHT. EXPECT TO SEE
SCATTERED SHOWERS AND A FEW STORMS SPREAD IN FROM THE WEST AS
WEAK FORCING FROM OVERNIGHT CONVECTION ADVECTS INTO THE AREA IN
CONCERT WITH A MINOR SHORT WAVE PRESSING IN FROM THE NORTHWEST. THIS
WILL FINALLY GIVE OUR WARM AND INCREASINGLY MOIST AIRMASS A REASON
TO PRECIPITATE. WILL TREND INCREASING POPS...ALTHOUGH STILL KEEPING
THEM IN THE CHANCE CATEGORY...THROUGH THE MORNING FROM THE WEST.
WILL NOT MAKE A LOT OF DISTINCTION ACROSS THE AREA AS IT IS
DIFFICULT TO PINPOINT AN AREA THAT MIGHT BE PARTICULARLY PRONE TO
INCREASED COVERAGE GIVEN THE RELATIVE UNIFORMITY OF THE AIRMASS AND
WEAKNESS OF THE FORCING. GUIDANCE HIGH TEMPS SEEM RATHER HIGH GIVEN
THE CLOUD TRENDS...THINK THAT AT LEAST THE NORTHWEST PIEDMONT
SHOULDN`T MAKE THE UPPER 80S AND WILL GO GENERALLY MID 80S ACROSS
THE BOARD.

BOTH THE GFS AND ECM SHOW A LULL ACROSS THE NORTHERN TIER TONIGHT
ACROSS THE NORTHERN TIER IN SUBSIDENCE BEHIND THE INITIAL UPPER
SHORT WAVE. THUNDER WILL BE TOUGH TO PRODUCE GIVEN SUBSIDENCE AND
UNFAVORABLE NOCTURNAL TREND. WILL TREND POPS FOR SHOWERS TOWARDS
THE SOUTHEAST. MINS WILL BE PERSISTENCE AND ON THE MILD SIDE...UPPER
60S.
-- End Changed Discussion --

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 240 AM MONDAY...

A SERIES OF DISTURBANCES ALOFT...WHICH HAVE TRENDED WEAKER IN NWP
GUIDANCE DURING THE PAST FEW DAYS AND WHOSE TIMING IS UNCERTAIN
GIVEN THE PROBABILITY OF BEING MODULATED BY UPSTREAM
CONVECTION...WILL MIGRATE THROUGH THE BASE OF A BROAD TROUGH ALOFT
EAST OF THE ROCKIES...AND ACROSS THE CENTRAL APPALACHIANS/NC THROUGH
WED. MEANWHILE AT THE SURFACE...A PRE-FRONTAL TROUGH OVER THE MIDDLE
ATLANTIC REGION THIS MORNING WILL STRENGTHEN THROUGH TUE...THEN BE
OVERTAKEN BY A COLD FRONT THAT WILL SETTLE SLOWLY SOUTHWARD FROM THE
MASON DIXON LINE TUE EVENING TO THE NC/SC LINE BY WED EVENING.

PRECIPITABLE WATER VALUES WILL CONSEQUENTLY REMAIN ABOVE
AVERAGE...BETWEEN 1.5 AND 1.8 INCHES... UNTIL FRONTAL PASSAGE. THE
DEEP MOISTURE AND ASSOCIATED UNINHIBITED CONDITIONAL INSTABILITY...
WHICH IS FORECAST TO MAXIMIZE IN THE 1000-1500 J/KG EACH
AFTERNOON...WILL SUPPORT NUMEROUS TO WIDESPREAD THUNDERSTORMS...WITH
COVERAGE DIMINISHING WITH NOCTURNAL COOLING TUE NIGHT...AND THEN
FROM NORTH TO SOUTH WITH THE FRONTAL PASSAGE ON WED. GIVEN THE
EXPECTATION OF WEAKER DISTURBANCES THAN PREVIOUSLY INDICATED...NOTED
ABOVE...MID LEVEL FLOW AND ASSOCIATED BULK SHEAR VALUES ARE NOW
FORECAST TO PEAK ONLY IN THE 20-25 KT RANGE...HIGHEST WED. AS
SUCH...ALREADY MINIMAL SEVERE POTENTIAL WILL BE FURTHER MUTED UNLESS
POCKETS OF STRONGER INSOLATION AND MODERATE INSTABILITY ARE
REALIZED...IN WHICH CASE A FEW STRONG-MARGINALLY SEVERE WET
MICROBURSTS WOULD BE PROBABLE. A MORE LIKELY SCENARIO REMAINS A
THREAT OF DOWNPOURS AND LOCALIZED FLOODING IN TRAINING
CONVECTION...OWING TO WSW MEAN FLOW ALIGNED PARALLEL TO THE MYRIAD
OF UNDERLYING SURFACE BOUNDARIES (TROUGH/EFFECTIVE FRONT-OUTFLOW
/ACTUAL FRONT...AND TO BACKBUILDING INDICATED BY SMALL FORECAST
CORFIDI VECTORS. ANY SUCH FLOODING WILL NOT BE WIDESPREAD...AND
INSTEAD CONFINED MOST LIKELY TO URBAN AREAS SINCE THE ANDREA-SOAKED
SOIL HAS DRIED IN THE PAST WEEK TO 10 DAYS...AND RESULTANT FLASH
FLOOD GUIDANCE VALUES HAVE INCREASED...INTO THE 2.5 TO 3 INCH RANGE
FOR ONE HOUR FOR EXAMPLE.

PROVIDED THERE ARE AT LEAST A FEW BREAKS IN OTHERWISE MOSTLY CLOUDY
SKIES AND CONVECTION...TEMPERATURES SHOULD CLIMB INTO THE LOWER TO
MIDDLE 80S...WARMEST SANDHILLS TUE. OTHERWISE...UPPER 70S WOULD BE
PROBABLE (IE. IN AREAS THAT EXPERIENCE MORE FREQUENT SHOWERS AND
STORMS). LOWS TUE NIGHT MOSTLY IN THE UPPER 60S...TO AROUND 70
DEGREES SOUTH...COOLING A CATEGORY TO TWO IN COOLER POST-FRONTAL NE
FLOW WED NIGHT.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 305 AM SUNDAY...

THU THROUGH FRI: BELOW AVERAGE TEMPERATURES - GENERALLY IN THE LOWER
TO MIDDLE 80S - IN WEAK POST-FRONTAL HIGH PRESSURE AND ASSOCIATED NE
TO EAST LOW LEVEL FLOW AND STABILITY...WILL THEN PREVAIL THROUGH THE
END OF THE WEEK. WILL ACCORDINGLY MAINTAIN THE FLAVOR OF PREVIOUS
GENERALLY DRY FORECASTS FOR THU-FRI...EXCEPT FOR THE SLIGHTEST OF
CHANCES ALONG THE FAR SOUTHERN AND WESTERN TIER...WHERE BOUNDARY
LAYER MOISTURE WOULD SUPPORT A LATE DAY SHOWER OR STORM. EVEN THAT
SLIGHT CHANCE MAY BE OVERDONE GIVEN AN APPARENT LACK OF TRIGGER
AMIDST DIVERGENT ANTICYCLONIC FLOW WITHIN THE AFOREMENTIONED SURFACE
RIDGE AXIS.

THIS WEEKEND: A SHALLOW UPPER LOW WILL HAVE DRIFTED INTO THE
SOUTHEAST STATES BY THE START OF THE WEEKEND...BUT INSTEAD OF
LIFTING TOWARD THE EAST COAST...GUIDANCE SUGGESTS THIS FEATURE WILL
MOVE WESTWARD AROUND THE SOUTHERN PERIPHERY OF A DEVELOPING
MID-UPPER RIDGE FROM THE SOUTHERN PLAINS TO THE MIDDLE ATLANTIC
REGION. AS SUCH...TEMPERATURES...AND HUMIDITY LEVELS WILL GRADUALLY
INCREASE IN INCREASINGLY SE TO SOUTHERLY RETURN FLOW. THE INCREASING
WARMTH AND HUMIDITY WILL ALSO SUPPORT A SLIGHT UPTICK IN PROBABILITY
OF PRECIPITATION...THOUGH STILL BELOW CLIMATOLOGICAL VALUES IN THE
20TH PERCENTILE GIVEN THE AFOREMENTIONED EXPANSION OF RIDGING
ALOFT...AND LACK OF LOW LEVEL FOCI OTHER THAN PERHAPS THE SEA
BREEZE.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
AS OF 140 AM MONDAY...

WARM...MOIST...BUT WEAKLY FORCED ENVIRONMENT WILL REMAIN OVER
CENTRAL NC THIS TAF PERIOD. CONDITIONS WILL REMAIN VFR THROUGH THE
PERIOD OUTSIDE OF CONVECTION.

EXPECT A GRADUAL INCREASE THIS MORNING IN MID LEVEL CLOUDINESS
ACROSS THE NORTHERN TIER OF THE AREA. WEAK FORCING FROM OVERNIGHT
CONVECTION IN WESTERN TN AND NORTHERN GA WILL BE MIGRATING INTO THE
WESTERN PIEDMONT THIS MORNING...WITH SCATTERED SHOWERS AT INT/GSO
AFTER SUNRISE...PERHAPS MID MORNING FURTHER EAST...RDU AND RWI.
DECENT INSTABILITY WILL SUPPORT MORE WIDESPREAD SHOWERS AND WIDELY
SCATTERED THUNDER THIS AFTERNOON...TSRA COVERAGE AND CONFIDENCE IN
TIMING/PLACEMENT PRECLUDE TAF INCLUSION AT THIS TIME. EXPECT A LULL
OVERNIGHT ALTHOUGH SCATTERED SHOWERS ARE EXPECTED. WINDS WILL BE
SOUTH TO SOUTHWEST AT LESS THAN 10KT.

ADDITIONAL DISTURBANCES WILL BE CROSSING THE AREA ALONG WITH A WEAK
COLD FRONT TUESDAY INTO WEDNESDAY...WITH PERIODS OF SHOWERS AND
STORMS PRODUCING SUB-VFR CONDITIONS. VFR CONDITIONS ARE
GENERALLY EXPECTED FROM THURSDAY ONWARD... OUTSIDE OF POSSIBLY SOME
EARLY MORNING STRATUS AND OR FOG DURING THE PRE-DAWN HOURS OF EACH
MORNING.

&&

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

&&

$$

SYNOPSIS...MLM
NEAR TERM...MLM
SHORT TERM...MWS
LONG TERM...MWS
AVIATION...MLM