Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 281818 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 218 PM EDT TUE APR 28 2015 .SYNOPSIS...A DRY AIRMASS IN PLACE ACROSS NORTH CAROLINA WILL STEADILY MOISTEN TONIGHT AND WEDNESDAY AS AN UPPER LEVEL DISTURBANCE AND ATTENDANT LOW PRESSURE SYSTEM TRACK EAST ALONG THE GULF COAST. && .NEAR TERM /TONIGHT THROUGH WEDNESDAY NIGHT/... AS OF 215 PM TUESDAY... THROUGH TONIGHT: THE DRY SFC RIDGE EXTENDING INTO THE CAROLINAS FROM THE NORTHWEST WILL GRADUALLY WEAKEN/MOISTEN THIS EVENING INTO TONIGHT AS A DEAMPLIFYING SOUTHERN STREAM SHORTWAVE TRACKS EASTWARD THROUGH THE LOWER MS RIVER VALLEY INTO THE DEEP SOUTH AND AN ATTENDANT SFC CYCLONE DEEPENS ALONG THE GULF COAST...REACHING THE FL PANHANDLE BY 12Z WED. EXPECT CLEAR SKIES WITH TEMPS IN THE MID/UPPER 60S THIS AFTERNOON...FOLLOWED BY A GRADUAL INCREASE IN CIRRUS THIS EVENING INTO TONIGHT AS UPPER LEVEL MOISTURE ADVECTS DOWNSTREAM OF THE DEVELOPING GULF COAST CYCLONE. IN CONTRAST TO 12Z 04/27 MODEL GUIDANCE...THE LATEST GUIDANCE INDICATES THE AFOREMENTIONED SURFACE LOW WILL TRACK VERY NEAR OR ALONG THE DEEP SOUTH GULF COAST TONIGHT...DELAYING AND/OR RESULTING IN MUCH WEAKER LOW-LEVEL WARM ADVECTION DOWNSTREAM ACROSS CENTRAL NORTH CAROLINA. AS A RESULT... EXPECT NO POTENTIAL FOR PRECIPITATION OVERNIGHT AS A SHORTWAVE RIDGE BUILDS OVER THE REGION (DOWNSTREAM OF THE GULF COAST LOW) AND A DRY LOW/MID-LEVEL AIRMASS PERSISTS. GIVEN INCREASE UPPER LEVEL CLOUD COVER...LOWS SHOULD BE WARMER THAN OBSERVED ON PREVIOUS NIGHTS...IN THE MID/UPPER 40S...COOLEST WHERE CIRRUS INCREASES LATER AND REMAINS THINNER. WED AND WED NIGHT: BELOW NORMAL CONFIDENCE WITH PRECIP TIMING/ AMOUNTS AND TEMPERATURES DUE TO A COMPLICATED UPPER LEVEL PATTERN OVER THE EASTERN US. 12Z MODEL GUIDANCE INDICATES RAPID DEAMPLIFICATION OF THE APPROACHING SOUTHERN STREAM WAVE PROGRESSING THROUGH THE DEEP SOUTH INTO THE SOUTHEAST DURING THE DAY WED...WITH AN ATTENDANT SFC LOW TRACKING ACROSS THE FL PANHANDLE AND OFFSHORE THE SE COAST WED NIGHT. PRECIPITATION CHANCES AND AMOUNTS WILL HIGHLY DEPEND UPON THE STRENGTH/ORIENTATION OF AN INVERTED TROUGH EXTENDING NORTHWARD FROM THE SFC LOW AS IT TRANSITIONS OFFSHORE LATE WED INTO WED NIGHT...ALONG WITH THE EVOLUTION OF THE UPPER LEVEL PATTERN IN TERMS OF THE INTERACTION BETWEEN NORTHERN STREAM SHORTWAVES DIGGING SOUTHWARD THROUGH THE OH/TN VALLEY AND THE DEAMPLIFYING SOUTHERN STREAM SHORTWAVE TRACKING TOWARD THE SOUTHEAST COAST. AT THIS TIME...EXPECT PRECIP CHANCES TO INCREASE FROM THE SOUTH/SW AFTER NOON...WITH THE BEST OVERALL CHANCE AND HIGHEST AMOUNTS (0.10-0.25") BETWEEN 21Z-06Z EAST OF HWY 1 WHEN/WHERE LOWER/UPPER LEVEL FORCING ARE MOST LIKELY TO BE JUXTAPOSED. HIGHS WED WILL VERY MUCH DEPEND UPON PRECIP /EVAP COOLING/. WILL INDICATE HIGHS RANGING FROM THE UPPER 50S SW PIEDMONT TO UPPER 60S FAR NE COASTAL PLAIN. LOWS WED NIGHT RANGING FROM THE UPPER 40S WESTERN PIEDMONT TO LOWER 50S COASTAL PLAIN. -VINCENT && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AS OF 200 PM TUESDAY... SURFACE LOW LIFTING UP THE ATLANTIC SEABOARD WILL WRAP MOISTURE INLAND AS FAR AS THE I95 CORRIDOR. MOISTURE ADVECTION WILL BE ACCOMPANIED BY H85 SPEED CONVERGENCE FROM THE OFFSHORE LOW INTO THE CORRIDOR AS WELL...WHICH WILL FURTHER ENHANCE THE CHANCE OF SHOWERS AS IT WILL BE AIDED ALOFT BY AN INITIAL UPPER SHORT WAVE WHICH WILL BE LIFTING NORTHEAST ACROSS THE AREA. INSTABILITY WILL BE MINIMAL FOR THUNDER...WILL THUS INCREASE CHANCES FOR SHOWERS TO LIKELY OVER THE EASTERN HALF OF THE AREA DURING THE MORNING. COOL AIRMASS WILL BE LOCKED IN PLACE BY EASTERLY FLOW WITH EVAPORATIVE COOLING AND NO INSOLATION...SO HIGHS WILL STRUGGLE TO REACH MID 60S. AN UPPER TROF WILL BE DIGGING SOUTHEAST OUT OF THE GREAT LAKES...AND BOTTOMING OUT ALONG THE NC/SC BORDER AS THE ASSOCIATED CLOSED LOW MOVES ACROSS THE AREA FRIDAY MORNING. THIS TROF WILL INCREASE THE CHANCE OF SHOWERS OVERNIGHT AND THROUGH THE DAY FRIDAY...ESPECIALLY ALONG THE NORTHERN TIER WHERE WESTERLY ELONGATION OF THE OFFSHORE SYSTEM WILL CONTINUE TO PRODUCE ONSHORE FLOW AND STRONG H85 CONVERGENCE. MID LEVEL INSTABILITY LOOKS GOOD WITH LAPSE RATES OF 6 TO 6.5K AND UPPER DIFFLUENCE WILL BE FAVORABLE AS THE UPPER 100KT JET TRANSLATES SOUTHEAST OF THE AREA. COULD SEE A STORM OR TWO...BUT THINKING OF MODERATE TO FAIRLY STRONG CONVECTIVE SHOWERS AT THIS POINT. THE TROF AXIS WILL MOVE OFFSHORE FRIDAY AFTERNOON...WITH DIMINISHING CLOUD COVERAGE LATE IN THE DAY AND CHANCES OF RAIN DWINDLING TO A SLIGHT CHANCE IN THE NORTHEAST BY MIDNIGHT FRIDAY NIGHT. COOL AIRMASS IN PLACE OVER THE AREA FRIDAY WILL BE REINFORCED BY DEEP NORTHERLY FLOW IN THE WAKE OF THE UPPER SYSTEM AND HIGHS WILL STALL AGAIN IN THE MID 60S. && .LONG TERM /SATURDAY THROUGH TUESDAY/... AS OF 200 PM TUESDAY... UPPER LOW LIFTS OUT FRIDAY NIGHT...WITH TRANQUIL WEATHER ON TAP THROUGH THE WEEKEND AND EARLY NEXT WEEK AS MILD HIGH PRESSURE BUILDS ACROSS THE AREA FROM THE LOWER MIDWEST. IN ADDITION TO COPIOUS INSOLATION...HEIGHTS WILL BE BUILDING ALOFT IN THE WAKE OF THE UPPER LOW AS WELL...SO WE CAN EXPECT A WELCOME WARMING TREND INTO EARLY NEXT WEEK. DRY WEATHER IS EXPECTED THROUGH THE PERIOD...ALTHOUGH HUMIDITY WILL BE INCREASING MONDAY AND TUESDAY AS THE SURFACE HIGH MOVES OFFSHORE AND WE SEE INCREASINGLY MOIST SOUTHERLY FLOW. HIGHS SATURDAY WILL BE SLIGHTLY BELOW NORMAL...GENERALLY 70 TO 75...WARMING TO SEASONAL ON SUNDAY...75 TO 80. A WARM HUMID AIRMASS WILL BE IN PLACE NEXT WEEK WITH HIGHS MONDAY AND TUESDAY FROM 80 TO 85. MINS WILL RANGE FROM THE UPPER 40S SATURDAY MORNING TO THE UPPER 50S BY TUESDAY MORNING. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... AS OF 110 PM TUESDAY... 24-HOUR TAF PERIOD: HIGH CONFIDENCE THAT VFR CONDITIONS WILL PREVAIL THROUGH AT LEAST THE OVERNIGHT HOURS...IF NOT THE ENTIRE 24 HOUR TAF PERIOD...ALTHOUGH HIGH CLOUDS WILL BE INCREASING AND CIGS LOWERING THROUGH THE PERIOD AS A LOW PRESSURE SYSTEM MOVES FROM THE GULF COAST TOWARD THE CAROLINA COAST. ASIDE FROM A FEW RANDOM GUSTS TODAY...WINDS SHOULD BE LIGHT AND VARIABLE DURING THE DAYTIME HOURS AND CALM TO LIGHT AND VARIABLE OVERNIGHT. THERE IS A CHANCE THAT RAIN COULD MOVE INTO THE SOUTH AND WEST BY 18Z WEDNESDAY...BUT THE HIGHER LIKELIHOOD IS THAT THEY WILL HOLD OFF UNTIL AFTER 18Z SO WILL LEAVE MENTION OUT FOR NOW. -RAH LOOKING AHEAD: RAIN IS EXPECTED TO MOVE INTO THE AREA FROM THE SOUTHWEST WEDNESDAY AFTERNOON...BRINGING OVERCAST SKIES AND LOWERING CIGS. THE NAM FORECAST SOUNDINGS ARE MORE EXCITED THAN THE GFS WITH RESPECT TO THE POSSIBILITY OF SUB-VFR CONDITIONS LATE WEDNESDAY INTO THURSDAY. THE CHANCE OF IFR CONDITIONS INCREASES LATE THURSDAY NIGHT INTO FRIDAY AS UPPER LEVEL LOW PRESSURE MOVES IN FROM THE NW. THE DEPARTURE OF THE LOW PRESSURE TO OUR EAST LATE FRI WILL BRING IMPROVING CONDITIONS BACK TO VFR LATE FRI THROUGH SAT AS HIGH PRESSURE BUILDS IN FROM THE WEST. -RAH/GIH && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...VINCENT SHORT TERM...MLM LONG TERM...MLM AVIATION...RAH/HARTFIELD

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