Area Forecast Discussion
Issued by NWS Wakefield, VA

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000 FXUS61 KAKQ 050121 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 821 PM EST WED MAR 4 2015 .SYNOPSIS...
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A COLD FRONT SLOWLY CROSSES THE REGION THROUGH TONIGHT. THE FRONT WILL STALL OVER NORTH CAROLINA ON THURSDAY...WITH A WAVE OF LOW PRESSURE MOVING ALONG THE FRONT THURSDAY AFTERNOON AND NIGHT. THIS WILL BRING ANOTHER ROUND OF WINTRY WEATHER TO THE AREA...FOLLOWED BY COLD AND DRY CONDITIONS BY FRIDAY. GRADUALLY MODERATING...MILDER TEMPERATURES ARE EXPECTED LATE IN THE WEEKEND INTO NEXT WEEK.
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&& .NEAR TERM /THROUGH THURSDAY NIGHT/...
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MADE SOME UPDATES TO POPS THIS EVENING...MAINLY TO SLOW THE PROGRESSION SOUTH OF THE HIGHER POPS TO KEEP ALL BUT NORTHERNMOST PORTIONS OF THE CWA DRY FOR THE NEXT FEW HRS. THIS BASED ON CURRENT RADAR TRENDS SHOWING PRECIP TENDING TO LIFT NORTH THROUGH 03Z WITH FIRST WAVE OF SFC LOW PRESSURE TRACKING ENE ACRS THE CWA (WITH PRECIP STAYING NORTH OF THE SFC LOW). THE PRECIP CURRENTLY OVER WRN VA/WV LOOKS POISED TO OVERSPREAD NORTHERN AREAS AFTER 03Z...AND SHIFT SOUTH INTO CENTRAL VA BETWEEN 04-06Z...THIS AS MAIN SFC LOW OVER THE NC/SC PIEDMONT BEGINS TO DEEPEN. ALSO ADDED FOG ACRS THE NORTH WHERE OBS ARE INDICATING VSBYS FROM 2SM DOWN TO 1/4SM IN SPOTS. EXPECT VSBYS TO IMPROVE SOMEWHAT LATER THIS EVENING AS WINDS INCREASE AND WIDESPREAD RAIN MOVES IN FROM THE NORTH (COULD SEE SOME LOCALLY DENSE FOG PUSH SOUTH INTO CENTRAL VA FOR A FEW HRS AS WELL). PREV DISCUSSION... LATEST WX ANALYSIS FEATURES A WELL DEFINED FRONTAL BOUNDARY OVER THE MID SOUTH/LWR OHIO VALLEY THAT SEEMS TO HAVE PHASED WITH ANOTHER, MORE DIFFUSE BOUNDARY STRETCHING FROM THE WV PANHANDLE INTO THE INTERIOR NORTHEAST. WEAK FORCING HAS GENERALLY KEPT PRECIP AT BAY THIS AFTERNOON. WHERE CAD WEDGE WAS ABLE TO BE FULLY ERODED ACROSS THE SOUTHERN CWA, TEMPS HAVE CLIMBED NICELY AS EXPECTED INTO THE U60S/L70S. POPS REMAIN 30-40% FOR SOME SPOTTY SHRAS ACROSS THE NORTH THROUGH EARLY EVENING, THOUGH WILL DEPICT GRADUAL RAMP UP OF POPS IN THE GRIDS THIS EVENING AND OVERNIGHT ACROSS THE NORTH AS FRONT TO THE NORTHWEST DROPS ACROSS THE AREA SLOWLY THROUGH LATE TONIGHT. MODELS REMAIN IN GOOD AGREEMENT WITH RESPECT TO FRONTAL TIMING, AND HAVE USED A GFS/NAM BLENDED SOLUTION FOR TIMING IN THE NEAR TERM. STILL EXPECTING INITIAL WAVE OF LOW PRESSURE TO MOVE SW TO NE ALONG THE FRONT AND TRACKS ACROSS THE CAROLINAS LATE TONIGHT INTO THURSDAY. MUCH COLDER AIR ARRIVES BEHIND THE FRONT WITH MOST OF THE AREA FALLING INTO THE UPPER 20S/LOW 30S BY THU AFTN. BUFR FORECAST SOUNDINGS CONTINUE TO DEPICT DRY AIR LINGERING BETWEEN 600-400MB TONIGHT...SO ANY PCPN (IN THE FORM OF -RA) OVERNIGHT WILL BE LIGHT. A STRONG ANTI-CYCLONIC JET IN PLACE FROM THE MID MISS VLY THROUGH ATLANTIC CANADA WILL TRANSLATE EWD THROUGH THE DAY THU AS A STRONG TROUGH DIGS ACROSS THE UPPER MIDWEST AND GREAT LAKES BY LATER THU MORNING INTO THU AFTERNOON. IT IS AT THIS TIME THAT DEEPER MOISTURE WILL ARRIVE AND RRQ FORCING WILL BE IDEALIZED, AS STRONG PV ANOMALY RIDES ACROSS THE AREA THU THROUGH THU NIGHT, TRIGGERING THE ONSET OF WINTRY PCPN FROM NW-SE ACROSS THE AREA. CRITICAL H85-7 THICKNESS VALUES (SUB 1540M) ARE NOT REALIZED UNTIL LATE IN THE AFTN THU INTO THU NIGHT OVER NORTHERN HALF OF THE AREA. HOWEVER...BY THIS TIME THE STRONGEST UVM WILL BE EXITING THE COAST. OVERALL, UTILIZING ROEBBER SLR FORECASTING TOOL ALONG WITH LOCAL THICKNESS CHART, FORECAST SLR VALUES WILL BE QUITE LOW FOR MUCH OF THE DAY (PERHAPS AS LOW AS 4:1-8:1). THIS MAKES SENSE GIVEN THAT THERE WILL BE A PROLONGED PERIOD OF SLEET (WHICH WILL EAT INTO SNOWFALL TOTALS)...AND THAT MID-LEVEL THICKNESSES WILL BE `WARM` DURING THE STRONGEST FORCING IN THE EARLY TO MID AFTERNOON HOURS. BASED ON ALL OF THE ABOVE, HAVE CONTINUED WITH A STRIPE OF 3-5" OF WET SNOW/SLEET ALONG A LINE FROM PALMYRA, VA TO TAPPAHANNOCK AND SALISBURY, MD. THIS IS BORDERED BY A BAND OF 2-3" FOR OTHER PORTIONS OF THE NW PIEDMONT...NRN NECK...NORTHERN RIC SUBURBS AND REMAINDER OF THE LOWER MD EASTERN SHORE. CURRENTLY 1-2" OF SLEET/SNOW IS FORECAST FROM THE SOUTHERN SECTIONS OF THE RIC METRO /TRI-CITIES DOWN THROUGH HAMPTON ROADS...WITH 1" OR LESS ALONG THE HIGHWAY 58 CORRIDOR OVER CENTRAL VA INTO THE PIEDMONT. THIS TRANSLATES TO WINTER STORM WARNINGS BEING HOISTED ALONG OUR NORTHERN TIER OF COUNTIES, WITH A TIER OF WINTER WEATHER ADVISORIES FOR THE RIC METRO AREA, THE PIEDMONT AND THE MIDDLE PENINSULA MAINLY ALONG AND NORTH OF A FARMVILLE TO PETERSBURG AND WILLIAMSBURG LINE. CONFIDENCE IS NOT HIGH ENOUGH TO CONTINUE ADVISORIES FARTHER SOUTH INTO SOUTH CENTRAL VA COUNTIES. GIVEN THAT ANY IMPACTS WOULD COME THURSDAY NIGHT IN THIS AREA, HAVE THEREFORE CONTINUED HWO MENTION GIVEN EXPECTATION OF SUB-ADVISORY CONDITIONS. WINTRY PCPN SHOULD TAPER OFF THU EVENING...AS TOP DOWN DRYING ENSUES W/DRIER AIR ARRIVING FROM THE NW DURING THE LATE EVENING. COULD SEE A BRIEF PERIOD OF FREEZING DRIZZLE LATE THU EVENING, HENCE DRAGGING ALL WINTER HEADLINES THROUGH MIDNIGHT THU NGT/FRI MORNING.
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&& .SHORT TERM /FRIDAY THROUGH SATURDAY/... HIGH PRESSURE/FAIR WEATHER TO PREVAIL DURING THE SHORT TERM. SHORTWAVE EXITS THE NE COAST FRI MORNING WITH CONFLUENCE ALOFT OVER THE MID-ATLANTIC. THIS WILL ALLOW STRONG 1030+MB ARCTIC HIGH PRESSURE TO CENTER OVER THE REGION FRI. COLD FRONT LOCATES OFFSHORE...EXTENDING SWWD INTO THE NRN GULF. BEST MOISTURE GETS SHUNTED OFFSHORE IN INCREASING WLY FLOW ALOFT. THE RESULT WILL BE DRY CONDITIONS...BUT WELL BELOW NORMAL TEMPERATURES. H85 TEMPS ~-8C AND LOW LEVEL THICKNESSES YIELD TEMPS IN THE LOW-MID 30S...POSSIBLY UPPER INTERIOR MD ERN SHORE. THE NEXT NRN STREAM SHORTWAVE CROSSES THE REGION FRI NIGHT...RESULTING IN LITTLE MORE THAN PARTLY CLOUDY SKIES. COLD FRI NIGHT WITH LOW GENERALLY MID TEENS TO AROUND 20. ZONAL FLOW DEVELOPS SUN AS HIGH PRESSURE REMAINS OVER THE REGION. SWLY RETURN FLOW COMMENCES...RESULTING IN MODERATING LOW LEVEL THICKNESSES AND TEMPS. THICKNESSES YIELD TEMPS IN THE LOW-MID 50S INLAND SUN...BUT GUIDANCE RUNNING IN THE MID-UPPER 40S. TRENDED TOWARD THICKNESSES...WITH HIGHS IN THE UPPER 40S-LOW 50S INLAND AND LOW TO MID 40S NEAR THE COAST...UNDER MOSTLY SUNNY TO PARTLY CLOUDY SKIES. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... GOING CLOSE TO THE 12Z GFS/CMC IN THE EXTENDED PERIOD. WILL MAINTAIN DRY WX FM SAT NGT THRU AT LEAST MON NGT AT THIS TIME..AS HI PRES WILL BE OVR THE AREA. THERE IS THEN A HINT OF LO PRES MOVNG NE OUT OF THE GULF AND ACRS THE REGION TUE THRU WED. FOR NOW...JUST HAVE SLGT CHC OF RAIN DURING THIS TIME. TEMPS WILL BE CLOSER TO SEASONABLE RDGS THRU THE PERIOD. MIN TEMPS WILL RANGE FM THE UPR 20S TO UPR 30S...AND MAX TEMPS WILL RANGE FM THE UPR 40S TO UPR 50S...MAYBE INTO THE 60S ON WED. && .AVIATION /01Z THURSDAY THROUGH MONDAY/...
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AS OF 01Z...COLD FRONT IS STILL NORTH OF THE AREA WITH VARIOUS BOUNDARIES SOUTH OF THE FRONT CAUSING VARIABLE WINDS AND FLIGHT CONDITIONS. LIFR CONDS AT SBY AND PHF ARE EXPECTED TO BE INTERMITTENT UNTIL THE COLD FRONT MOVES FROM NORTH TO SOUTH ACRS THE TAF SITES DURING THE EARLY MORNING HOURS. FOLLOWING THE FRONTAL PASSAGE...MVFR/IFR CIGS BECOME SOLIDLY IFR/LIFR TOWARD MORNING AS RAIN DEVELOPS. RAIN MIXES WITH FREEZING RAIN AND SLEET FOR A PERIOD OF TIME BEFORE TRANSITIONING TO SNOW WITH THE CHANGE OCCURRING FROM NORTH TO SOUTH DURING THE DAY THURSDAY. TWO TO FOUR INCH SNOW ACCUMULATIONS ARE EXPECTED AT RIC AND SBY WITH AN INCH OR LESS AT THE SE TAF SITES. WINDS WILL BE GUSTY FROM THE NORTH MUCH OF THE DAY. OUTLOOK...PCPN MOVES OFF TO THE EAST THURSDAY EVENING AND VFR RETURNS. GOOD WEATHER IS EXPECTED FRIDAY INTO EARLY NEXT WEEK.
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&& .MARINE... A COLD FRNT WILL DROP ACRS THE WTRS LATER THIS EVENG INTO THU MORNG...AS SEVERAL WEAK WAVES OF LO PRES MOVE NE ALNG THE BNDRY. AS THE FRNT PUSHES SE OF THE AREA TNGT...SCA CONDS WILL COMMENCE OVR THE WTRS. THESE CONDS WILL CONTINUE THRU FRI MORNG AND INTO THE AFTN FOR THE CSTL WTRS. WINDS MAY COME CLOSE TO GALE FORCE OVR SRN CSTL WTRS...BUT CONFIDENCE IS STILL NOT HI ENUF TO ISSUE A GALE WARNG ATTM. ALSO KEPT ALL RIVER ZNS EXCEPT THE LWR JAMES OUT OF THE ADVSRY FOR NOW...BUT WILL CONTINUE TO MONITOR. WAVES OVER THE CHES BAY WILL BLD TO 3-5 FT...WITH SEAS OVER CSTL WTRS BLDNG TO 6-8 FT. SFC HI PRES THEN BLDS IN FOR FRI INTO THE WEEKEND LEADING TO IMPROVING MARINE CONDS. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...WINTER STORM WARNING FROM 6 AM THURSDAY TO MIDNIGHT EST THURSDAY NIGHT FOR MDZ021>025. NC...NONE. VA...WINTER WEATHER ADVISORY FROM 6 AM THURSDAY TO MIDNIGHT EST THURSDAY NIGHT FOR VAZ060>062-067>073-077-078-080>086-090- 099. WINTER STORM WARNING FROM 6 AM THURSDAY TO MIDNIGHT EST THURSDAY NIGHT FOR VAZ048-049-063-064-074>076. MARINE...SMALL CRAFT ADVISORY UNTIL 1 PM EST FRIDAY FOR ANZ650-652-654. SMALL CRAFT ADVISORY UNTIL 4 PM EST FRIDAY FOR ANZ656-658. SMALL CRAFT ADVISORY FROM 4 AM THURSDAY TO 10 AM EST FRIDAY FOR ANZ630>632-634. SMALL CRAFT ADVISORY FROM 7 AM THURSDAY TO 10 AM EST FRIDAY FOR ANZ633-638. && $$ SYNOPSIS...MAM NEAR TERM...AJZ/LKB/MAM SHORT TERM...SAM LONG TERM...SAM/TMG AVIATION...SAM MARINE...TMG

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