Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 271102
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
700 AM EDT MON JUL 27 2015

.SYNOPSIS...SURFACE HIGH PRESSURE WILL RETREAT OFFSHORE TODAY. A
COUPLE OF WEAK DISTURBANCES IN NORTHWEST FLOW ALOFT WILL THEN CROSS
THE REGION THROUGH THE MIDDLE OF THE WEEK.


&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 400 AM MONDAY...

WEAK HIGH PRESSURE RIDGE OVER THE AREA THIS MORNING WILL SHIFT
OFFSHORE TODAY...WHILE A SERIES OF WEAK DISTURBANCES APPROACH IN
NORTHWESTERLY FLOW ALOFT.  DEEP MIXING TO JUST ABOVE 850MB AND
RELATIVELY DRY BOUNDARY LAYER AIR WILL LIMIT THE POTENTIAL DEWPOINT
RECOVERY TODAY...WHILE MID-LEVEL LAPSE RATES REMAIN WEAK AND THE
STEEPER LAPSE RATES OVER THE OHIO VALLEY (6-6.5 C/KM OBSERVED AT
KILN) STAY TO OUR NORTH.  THUS...FORECAST INSTABILITY OVER CENTRAL
NC IS WEAK TODAY...300-600 J/KG AT BEST PER NAM/GFS BUFR SOUNDINGS.

A STRONG SPEED MAX CROSSING THE MOUNTAINS AND DIFFERENTIAL HEATING
SHOULD TRIGGER SCATTERED CONVECTION IN THE MOUNTAINS..WHICH WILL
HAVE THE PROPENSITY TO DRIFT SOUTHEAST INTO PIEDMONT THIS EVENING.
WITH A LESS FAVORABLE ENVIRONMENT DOWNSTREAM...CONVECTION IS NOT
EXPECTED TO MAKE IT FURTHER THAN THE TRIANGLE...IF IT MAKES IT THAT
FAR...SO WILL KEEP A CHANCE POP FOR THE TRIAD AREA AND NORTHER
PIEDMONT THROUGH LATE EVENING.

HIGH CLOUDS POURING IN FROM THE NORTHWEST COULD PROVE TRICKY FOR
HIGHS TODAY..BUT AT THE MOMENT THEY DO NOT APPEAR WIDESPREAD TO
LIMIT FULL HEATING...WHICH SHOULD YIELD HIGHS IN THE 89-93 RANGE.

&&

.SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
AS OF 400 AM MONDAY...

NORTHWEST FLOW ALOFT CONTINUES ON TUESDAY...THOUGH HEIGHTS ALOFT
ALSO START TO RISE SLIGHTLY IN RESPONSE TO AN EASTWARD SHIFT OF THE
CENTRAL US RIDGE AXIS.  CONTINUED MOISTENING IN THE LOW-LEVELS WILL
SUPPORT BETTER INSTABILITY THAN TODAY DESPITE WEAK LAPSE RATES.  THE
MAIN TRIGGERS FOR CONVECTION WILL AGAIN BE TERRAIN INDUCED
CIRCULATION AND THE FLOW OF WEAK DISTURBANCES ALOFT.  WITH BETTER
INSTABILITY FORECAST..HOWEVER...WIDELY SCATTERED CONVECTION SEEMS
POSSIBLE ACROSS MOST OF CENTRAL NC WITH HIGHER CONFIDENCE IN THE
WESTERN PIEDMONT.  HIGHS MAY BE A DEGREE OR TWO COOLER ON TUESDAY
GIVEN INCREASED CLOUD COVER...BUT STILL INT HE UPPER 80S AND LOWER
90S.  THE COVERAGE OF STORMS WILL LESSEN TUESDAY EVENING WITH LOSS
OF HEATING...BUT GUIDANCE SUGGESTS A FEW STORMS COULD CONTINUE TO
PERCOLATE WELL INTO THE NIGHT...ESPECIALLY OVER THE SOUTHERN AND
WESTERN PIEDMONT AREAS.  LOWS MORE SOLIDLY IN THE LOWER 70S.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
AS OF 400 AM MONDAY...

A SUB-TROPICAL RIDGE CENTERED OVER THE SOUTHERN PLAINS AND MID-MS
VALLEY WILL RETROGRESS INTO THE FOUR CORNERS REGION AND CONSEQUENTLY
ALLOW A PROGRESSION OF SHORTWAVE TROUGHS TO CARVE A MEAN TROUGH OVER
THE EASTERN US. AFTER THE DOMINANCE OF AN APPALACHIAN LEE TROUGH...
BUT RELATIVELY MINIMAL CONVECTIVE DEVELOPMENT OWING TO WEAK LAPSE
RATES ALOFT DURING THE MIDDLE OF THE WEEK...THE MODELS ARE IN GOOD
AGREEMENT THAT A COLD FRONT RELATED TO THE PROGRESSION OF A LEAD
SHORTWAVE TROUGH ACROSS THE GREAT LAKES WILL SETTLE EAST OF THE
APPALACHIANS LATE THU-FRI...AT WHICH TIME SCATTERED SHOWERS AND
STORMS ARE EXPECTED THROUGHOUT CENTRAL NC.

THEREAFTER...THERE ARE MIXED SIGNALS REGARDING THE PROBABILITY OF
PRECIPITATION THROUGH THE WEEKEND. THE OVERALL CONFIGURATION OF A
TROUGH ALOFT IN THE EASTERN US SHOULD SUPPORT ABOVE AVERAGE CHANCES
OF PRECIPITATION...BUT THE MODELS INDICATE THE LOW LEVEL FRONTAL
ZONE MAY SETTLE JUST SOUTHEAST OF CENTRAL NC...WHICH WOULD TEND TO
SUPPRESS THE BRUNT OF THE SHOWERS AND STORMS OVER THE SOUTHEASTERN
PART OF THE STATE. GIVEN THE SOMEWHAT CONFLICTING SIGNALS...THIS
FORECAST WILL BE WEIGHTED TOWARD CONTINUITY FROM THE PREVIOUS
FORECASTS - SLIGHT TO CHANCE POP...HIGHEST SOUTHEAST AND MAXIMIZED
DURING THE AFTERNOON AND EVENING.

TEMPERATURES WILL PEAK MAINLY IN THE LOWER 90S DURING MID-
WEEK...THEN TREND TO AOB AVERAGE FOR THE WEEKEND. LOWS AROUND 70.

&&


.AVIATION /12Z MONDAY THROUGH FRIDAY/...
AS OF 655 AM MONDAY...

JUST A COUPLE AREAS REPORTING IFR VSBYS THIS MORNING...INCLUDING
KFAY AND KRWI.  THESE VSBYS WILL IMPROVE TO VFR SHORTLY AFTER
12Z...WHILE MID AND HIGH CLOUDS CONTINUE TO POUR IN FROM THE
NORTHWEST.  VFR CONDITIONS WILL CONTINUE THROUGH THE
AFTERNOON...WITH JUST A CHANCE OF A STORM AROUND KGSO AND/OR KINT
LATER THIS AFTERNOON AND EVENING.  THE CHANCE OF ANY STORMS MOVING
EAST TOWARD KRDU IS LOW AND NO MENTION OF TSRA WILL BE INCLUDED IN
THE CURRENT TAF.

TONIGHT..WINDS WILL AGAIN BE LIGHT/VARIABLE...WHICH WILL PAVE THE
WAY FOR SOME POSSIBLE FOG/STRATUS...MAINLY ACROSS THE COASTAL PLAN
BASED ON MOST GUIDANCE.  IMPACTS ARE NOT EXPECTED TO BE
WIDESPREAD...AND CONFIDENCE IS AVERAGE AT THIS POINT.

OUTLOOK...INCREASING MOISTURE WILL LEAD TO BETTER CHANCE OF EARLY
MORNING (09-13Z) STRATUS/FOG FROM TUESDAY ONWARD. MEANWHILE...
AFTERNOON STORMS WILL ALSO BE POSSIBLE...ESPECIALLY AS A COUPLE
DISTURBANCES CROSS THE AREA IN NORTHWESTERLY FLOW ALOFT.  A COLD
FRONT WILL APPROACH THE AREA LATE IN THE WEEK AND MAY BRING A BETTER
CHANCE OF CONVECTION AND ADVERSE AVIATION CONDITIONS.

&&

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

&&

$$

SYNOPSIS...22
NEAR TERM...22
SHORT TERM...22
LONG TERM...26
AVIATION...22



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