AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 747 AM EDT TUE MAR 18 2014 .SYNOPSIS...A LATE SEASON COLD AIR DAMMING WEDGE WILL REMAIN IN PLACE THROUGH WEDNESDAY AS MODIFIED ARCTIC HIGH PRESSURE EXTENDS SOUTHWARD INTO THE REGION AND MULTIPLE WAVES OF LOW PRESSURE DEVELOP ALONG AND OFFSHORE THE CAROLINA COAST. && .NEAR TERM /TODAY/... AS OF 335 AM TUESDAY... OVERVIEW: A COLD AIR DAMMING WEDGE WILL REMAIN SOLIDLY IN PLACE ACROSS CENTRAL NC TODAY...BETWEEN A LOW PRESSURE SYSTEM STRENGTHENING OFFSHORE THE SE/CAROLINA COAST AND MODIFIED ARCTIC HIGH PRESSURE EXTENDING INTO THE REGION FROM THE NORTH. PRECIPITATION: EXPECT THE BEST CHANCE FOR MEASURABLE PRECIPITATION TO GRADUALLY SHIFT EASTWARD TODAY AS A SHEAR AXIS (ON THE NORTHERN PERIPHERY OF THE SOUTHERN STREAM UPPER LOW IN WESTERN NC AT 06Z) AND DRIER MID-LEVEL AIRMASS APPROACH FROM THE WEST EARLY THIS MORNING... THOUGH TRENDS IN WV IMAGERY BETWEEN 00-06Z SUGGEST ADVECTION OF THE DRIER MID-LEVEL AIRMASS MAY BE DELAYED THROUGH EARLY/MID AFTERNOON DUE TO INCREASING MID-LEVEL MOISTURE ASSOCIATED WITH THE SOUTHERN STREAM UPPER LOW AND ATTENDANT SFC CYCLONE TRACKING NORTHEAST ACROSS SOUTHERN GA AND OFFSHORE THE SOUTHEAST COAST BY ~18Z. FORCING FOR ASCENT LATE THIS MORNING THROUGH MID AFTERNOON WILL BE PRESENT OVER EASTERN PORTIONS OF THE STATE IN THE FORM OF LOW-LEVEL WARM ADVECTION AND FRONTOGENESIS AS LOW/MID-LEVEL FLOW BACKS AND STRENGTHENS FROM THE EAST ACROSS EASTERN/COASTAL PORTIONS OF NC...IN ADDITION TO DPVA ASSOC/W THE WEAKENING SHEAR AXIS AND PERHAPS A GLANCING BOUT OF DPVA ALONG THE NORTHERN PERIPHERY OF THE UPPER LEVEL LOW AS IT TRACKS OFFSHORE THE SOUTHEAST COAST. TEMPERATURES: HAVE DECREASED HIGHS BY AS MUCH AS 5-10F FROM PRIOR FORECASTS FOR TODAY...RANGING FROM THE MID 30S N/NW PIEDMONT TO ~40F IN THE SOUTH. DESPITE MID-MARCH INSOLATION AND ARGUABLY A SHALLOWER DEPTH OF MOISTURE IN COMPARISON TO YESTERDAY (ESP WEST)...GIVEN THE UNSEASONABLY STRONG COLD AIR DAMMING WEDGE IN PLACE...PERSISTENT N/NNE LOW-LEVEL FLOW...WEAK/SHALLOW COLD ADVECTION...AND PERIODIC WETBULBING ASSOCIATED WITH LIGHT PRECIP (ESP EAST)...FEEL THAT ANY WARMING ASSOC/W THE FORMER MAY WELL BE OFFSET BY THE LATTER. PTYPE/WINTER WEATHER ADVISORY: FREEZING DRIZZLE (PERHAPS PERIODS OF LIGHT FREEZING RAIN TRIANGLE NORTH AND NE) WILL PERSIST ACROSS THE ADVISORY AREA UNTIL TEMPERATURES WARM ABOVE FREEZING BY EARLY AFTERNOON. IT IS POSSIBLE THAT TEMPS COULD BE SLIGHTLY COOLER OR WARMER THAN CURRENTLY INDICATED BY 16Z...AND THAT THE END TIME OF THE WINTER WEATHER ADVISORY (NOON) COULD BE A FEW HRS OFF IN EITHER DIRECTION DEPENDING ON THE VARIETY OF FACTORS MENTIONED ABOVE. EITHER WAY...ADDITIONAL ICE ACCUMULATIONS SHOULD RANGE FROM A TRACE TO A FEW HUNDREDTHS OF AN INCH...OF WHICH THE HIGHER END OF THAT RANGE SHOULD REMAIN CONFINED ACROSS PORTIONS OF THE TRIANGLE AND NE COASTAL PLAIN. -VINCENT && .SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/... AS OF 300 AM TUESDAY... COLD RIDGING REMAINS IN PLACE TONIGHT WITH A LOW AMPLITUDE SHORT WAVE RIDGE AND DRYING ALOFT. FLOW ATOP THE COLD DOME VEERS SOUTHERLY AND STRENGTHENS OVERNIGHT...WHILE THE SATURATED PORTION OF THE MOISTURE PROFILE CUTS OFF AROUND 6KFT. ISENTROPIC LIFT WILL BE WEAK FROM THE SOUTHEAST EARLY OVERNIGHT AS THE FLOW SWINGS AROUND...HENCE PRECIP WILL BE PATCHY AND LIGHT WITH AN ASSOCIATED TEMP PROFILE IN THE LIQUID RANGE. NEAR NEUTRAL ADVECTION AND LOSS OF REINFORCING EVAPORATIVE COOLING WILL MAINTAIN TEMPS NEARLY STEADY FROM 35 TO 40. EROSION OF THE CAD WILL BE UNDERWAY EARLY WEDNESDAY...WITH DEEP SOUTHWEST WARM AIR ADVECTION AHEAD OF AN APPROACHING `COLD` FRONT. DYNAMICS WILL BE WEAK WITH THE PARENT SYSTEM WELL NORTH OF THE AREA AND MOISTURE WILL BE LIMITED AHEAD OF THE FRONT WITH WESTERLY FLOW ACROSS THE NORTHERN GULF...HENCE ONLY A SLIGHT CHANCE OF SHOWERS. TEMPERATURES WILL RISE DRAMATICALLY AS EROSION OF THE COLD AIR FROM THE SOUTH AND WEST WILL PROMOTE A FAST WARMUP ALONG THE FRINGES... AND THERE COULD BE SOME BREAKS IN THE CLOUDINESS AS WELL. TIMING THE WARMUP IS A PROBLEMATIC...AND THE NORTHEAST COULD SEE WARMUP DELAYED TIL LATER AFTERNOON. REGARDLESS...HIGHS IN THE 50S WILL BE WELCOMED AFTER THE PAST COUPLE OF DAYS. ANOTHER COOL NIGHT IS ON TAP WITH POST FROPA COLD AIR ADVECTION WEDNESDAY NIGHT. MINS WILL FALL TO 40 TO 45...WITH SKIES BECOMING MOSTLY CLEAR. -MLM && .LONG TERM /THURSDAY THROUGH MONDAY/... AS OF 230 AM TUESDAY... THURSDAY AND THURSDAY NIGHT...BROAD UPPER TROF PASSES BY ALOFT... WITH HEIGHTS BEGINNING TO BUILD AND MILD HIGH PRESSURE EDGES IN FROM THE SOUTHWEST. LOOKING AT MOSTLY SUNNY SKIES WITH HIGHS REACHING THE MID 60S THURSDAY. GOOD RADIATION CONDITIONS PROMOTE A F FRIDAY AND SATURDAY: FRIDAY LOOKS VERY PLEASANT AT THIS TIME AS CENTRAL NORTH CAROLINA WILL BE IN A SOUTHWEST FLOW REGIME ON THE BACK SIDE OF A SURFACE HIGH PRESSURE THAT WILL BE MOVING OUT INTO THE WESTERN ATLANTIC. FLOW ALOFT WILL BE VERY ZONAL. MOSTLY CLEAR SKIES WILL DOMINATE WITH TEMPERATURES IN THE UPPER 60S TO LOW 70S AND LOWS NEAR 50 DEGREES FRIDAY NIGHT WITH INCREASING CLOUDINESS BY DAYBREAK ON SATURDAY. PARTLY TO MOSTLY CLOUDY SKIES WILL PREVAIL ON SATURDAY AS A SURFACE LOW PRESSURE SYSTEM MOVES THROUGH THE GREAT LAKES WITH ATTENDANT FRONT APPROACHING FROM THE WEST. WARM SOUTHWESTERLY FLOW WILL CONTINUE OUT AHEAD OF THE FRONT WHICH DESPITE THE CLOUDS...WILL ALLOW TEMPERATURES TO CLIMB ONCE AGAIN INTO THE UPPER 60S TO LOWER 70S NW TO SE. FRONT IS PROGGED TO CROSS THROUGH CENTRAL NC NEAR 00Z SUNDAY. DESPITE THE FAVORABLE DIURNAL TIMING...MODEL SOLUTIONS DIFFER AS TO THE AMOUNT OF QPF...IF ANY DURING FRONTAL PASSAGE. THE GFS IS THE WETTER SOLUTION WITH THE ECMWF COMING THROUGH AS MOSTLY DRY. FORECAST SOUNDINGS SHOW SOME VERY WEAK INSTABILITY SATURDAY EVENING WITH SB CAPE VALUES LESS THAN 300 J/KG WITH BULK SHEAR VALUES OF 30-40 KTS. WILL KEEP CONVECTIVE SHOWERS IN AS THE PREDOMINANT WEATHER TYPE AT THIS TIME EVEN THOUGH AN OUTSIDE POSSIBILITY OF THUNDER REMAINS. NORTHWESTERLY FLOW WILL ENSUE AFTER FRONTAL PASSAGE AND COLD AIR ADVECTION WILL BEGIN...KNOCKING LOW TEMPERATURES DOWN ABOUT 10 DEGREES LOWER THAN FRIDAY NIGHT...MID 30S TO LOWER 40S. SUNDAY THROUGH MONDAY NIGHT: COOLER DAY FOR SUNDAY AS NORTHEASTERLY FLOW TAKES OVER AT THE SURFACE AND HIGHS SCALE BACK TO THE MID 50S TO NEAR 60 DEGREES...DESPITE MOSTLY CLEAR SKIES. WILL STILL BE ON THE FRONT SIDE OF THE UPPER LEVEL TROUGH HOWEVER AS THIS WILL NOT CROSS THE AREA UNTIL SUNDAY NIGHT AND WITH IT A REINFORCING DRY COLD FRONT AT THE SURFACE. ONCE THIS MOVES THROUGH NORTHERLY FLOW AT THE SURFACE AND NW FLOW ALOFT WILL BRING LOW TEMPERATURES DOWN INTO THE LOW TO MID 30S. ON MONDAY...A 1025 MB HIGH PRESSURE WILL MOVE ACROSS THE NORTHEASTERN STATES...KEEPING CONDITIONS DRY BUT COOL ACROSS CENTRAL NC. AS THE HIGH MOVES INTO A FAVORABLE LOCATION FOR HYBRID DAMMING...CLOUD COVER WILL INCREASE ACROSS THE STATE FROM THE WEST. WHILE A WEDGE FRONT WILL DEVELOP...THE STRENGTH OF THE HIGH IS WEAKER THAN OPTIMAL FOR HYBRID CAD WHICH MAY TAME THE EFFECTS OF IT A LITTLE BIT. REGARDLESS...COOLER HIGHS IN THE LOW TO MID 50S WITH LOWS MONDAY NIGHT IN THE MID TO UPPER 30S. THERE IS QUESTION IN THE MODELS ON WHETHER OR NOT PRECIPITATION WILL BE APPROACHING THE AREA BETWEEN A STRONG LOW OVER THE UPPER MIDWEST AND A DEVELOPING LOW IN THE SW ATLANTIC. ECMWF IS DRY AT THIS TIME WITH THE GFS SUPPORTING A WETTER SOLUTION. CONFIDENCE IN EITHER RUN IS VERY LOW AT THIS TIME AND THEREFORE WILL KEEP THE FORECAST DRY FOR NOW. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... AS OF 745 AM TUESDAY... 24-HR TAF PERIOD: IFR/MVFR CONDITIONS (CEILINGS 500-1200 FT AGL) WILL PREVAIL THROUGH THE TAF PERIOD IN ASSOCIATION WITH A COLD AIR DAMMING WEDGE IN PLACE ACROSS THE REGION AND A DEEPENING LOW PRESSURE SYSTEM JUST OFFSHORE THE SOUTHEAST COAST. LIGHT FZDZ/FZRA WILL REMAIN POSSIBLE AT THE INT/GSO/RDU/RWI TERMINALS THROUGH 16Z... WITH RA/DZ FURTHER SOUTH AT THE FAY TERMINAL WHERE TEMPS ARE NOT EXPECTED TO FALL BELOW FREEZING. LOOKING AHEAD: IFR/MVFR CEILINGS WILL LIKELY PERSIST THROUGH THE DAY WEDNESDAY IN ASSOCIATION WITH A LINGERING COLD AIR DAMMING WEDGE ACROSS THE AREA. SHOWER ACTIVITY WILL BE POSSIBLE WED NIGHT/THU MORNING AS A WEAK FRONT APPROACHES FROM THE WEST...WITH A RETURN TO VFR CONDITIONS BY SUNRISE THU. -VINCENT && .CLIMATE... THE RECORD LOW MAXIMUM TEMPERATURES FOR MARCH 18 (TUESDAY) ARE... KGSO...36 DEGREES FROM 1961. KRDU...36 DEGREES FROM 1892. KFAY...41 DEGREES FROM 1998. && .RAH WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO NOON EDT TUESDAY FOR NCZ011-026>028-040>043-073>077. WINTER WEATHER ADVISORY UNTIL NOON EDT TUESDAY FOR NCZ007>010- 021>025-038-039. &&
Posted on: Tue, 18 Mar 2014 11:59:49 +0000
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