Area Forecast Discussion
Issued by NWS Wakefield, VA

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731 FXUS61 KAKQ 130859 AFDAKQ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 359 AM EST SAT FEB 13 2016 .SYNOPSIS... ARCTIC HIGH PRESSURE BUILDS ACROSS THE REGION THROUGH TONIGHT...THEN MOVES OFF THE MID ATLANTIC COAST LATE SUNDAY. LOW PRESSURE OVER THE DEEP SOUTH MONDAY...LIFTS NORTHEAST ACROSS THE MID ATLANTIC REGION TUESDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... COLD FRONT MOVES OFFSHORE EARLY THIS MORNING WITH ARCTIC HIGH PRESSURE BUILDING INTO THE REGION FROM THE NW. DESPITE PLENTY OF SUN...A VERY COLD DAY ON TAP AS H85 TEMPS PLUMMET TO ARND MINUS 18 TO MINUS 20C (-2 TO -3 STD DEV). STRNG CAA WILL ADD A WIND CHILL COMPONENT TO THE MIX WITH NW WINDS AVGG 15 TO 25 MPH WITH GUSTS 30 TO 35 MPH. GUSTS OVER THE EASTERN SHORE AND COASTAL AREAS EXPECTED TO REACH 40 MPH. EXPECT WIND CHILLS BETWEEN 10-15 DEGREES NORTH TO 15-20 DEGREES SOUTH. BAY INDUCED SC STREAMERS WILL LIKELY DVLP OVR THE CHES BAY / DELMARVA REGIONS BUT EXPECT THE DRY AIRMASS (DP TMPS ARND ZERO) TO PREVENT ANY SNOW SHWRS FROM DVLPNG. HIGHS FROM THE M20S NORTH TO L30S SOUTH. && .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/... 1035 MB ARCTIC HIGH MOVES INTO THE OHIO/TN VLLYS THIS EVENING WITH THE CENTER OF THE HIGH OVER WEST VA BY 12Z SUN. NW WINDS CONT AS RIDGE AXIS REMAINS WEST OF THE FA. HOWEVER...THE HIGH GETS CLOSE ENUF FOR WINDS TO DIMINISH ACROSS THE PIEDMONT. THIS ALLOWS FOR DECENT RADIATIONAL COOLING TO OCCUR UNDER MAINLY CLR SKIES. LOWS PLUNGE INTO THE SINGLE DIGITS TO LOW TEENS INLAND TO UPPER TEENS NEAR THE COAST. WIND CHILL VALUES GENERALLY 0 TO 5 ABOVE INLAND AND AROUND 5 BELOW NRN NECK TO THE ERN SHORE. HAVE ISSUED A WIND CHILL ADVISORY WHERE READINGS ARE EXPECTED TO DROP BLO ZERO. CENTER OF ARCTIC HIGH MOVES ACROSS THE FA SUN...THEN OFF THE COAST SUN EVE. TSCTNS SHOW CLR SKIES TO START BUT HIGH LVL MSTR QUICKLY OVRSPRDS THE RGN WEST TO EAST DURING THE AFTRN HRS AHEAD OF THE NEXT SYSTM APPRCHG FROM THE WEST. HIGHS ONLY WARM INTO THE M-U20S (-2 STD DEV)...EXCEPT ARND 30 SWRN MOST CNTYS BUT WITH MUCH LESS WIND. SFC HIGH SHIFTS TOWARD NEW ENGLAND SUN NIGHT AS THE NEXT STORM SYSTEM DEVELOPS OVER THE DEEP SOUTH MONDAY. NRN STREAM ENERGY LIFTS NORTH OF THE REGION SUN NIGHT/MONDAY AS A MID LEVEL TROUGH TRACKS ACROSS THE CENTRAL CONUS MON. SWLY FLOW ALOFT WILL RESULT IN MOISTURE RETURN INTO THE MID-ATLANTIC REGION. POPS INCREASE AFTR MIDNIGHT (CHC POPS MOST AREAS XCPT LIKELY NWR MOST CNTYS) LATE SUN NIGHT AS THE NRN STREAM SYSTEM WEAKENS AND WEAK ISENTROPIC LIFT ADVECTS INTO THE REGION. AIR MASS COLD ENOUGH FOR ALL SNOW AS LOWS SUN NIGHT IN THE UPPER TEENS TO ARND 20. GIVEN LGHT QPF AMTS (LESS THAN .10) SNOW AMTS BY 12Z MON XPCTD TO BE LESS THAN ONE INCH. PRECIP CHANCES QUICKLY INCREASE MON AS A COASTAL TROUGH SHARPENS ALONG THE COAST AND THE AFOREMENTIONED DEEP SOUTH LOW BEGINS TO LIFT NEWD TOWARD THE LOCAL AREA. CHC TO LIKELY POPS WILL BE MAINTAINED DURING THE MORNING INCREASING TO LIKELY TO CATEGORICAL DURING THE AFTRN. THE CHALLENGING PART OF THIS FCST WILL BE PCPN TYPE AS THE ENTIRE GAMBIT OF PCPN TYPES ARE EXPECTED DUE TO WAA ALOFT AND CRITICAL THICKNESSES INDICATING A CHANGE OVER FROM SN TO A MIX OF SN/IP/FZRA LATE MON MORNING ACROSS THE PIEDMONT TO MAINLY RAIN BY 00Z TUE AS TMPS RISE ABOVE FREEZING. LTST DATA SPRTS LOUISA/FLUVANNA CNTYS HOVER ARND FREEZING WELL INTO MON NIGHT. THIS WOULD LEAD TO FROZEN PCPN TYPES THERE MUCH FOR A LONGER PERIOD OF TIME. BUFKIT THERMAL PROFILES SUPORT ANY ICING (FREEZING RAIN) MAINLY WEST OF THE I95 CORRIDOR. GIVEN MORE ICE POTENTIAL...THE TOTAL SNOW ACCUMLS WILL BE HELD DOWN TO 1-2 INCHES OVR THE WRN MOST CNTYS WITH AN INCH OR LESS ELSEWHERE...BUT THE ICING POTENTIAL WILL INCREASE. ICING AMTS EXPECTED TO RANGE LESS THAN .05 ALONG THE I95 CORRIDOR UPWARDS TO .10 FROM FVX-LKU. PCPN TYPE BECOMES MOSTLY LIQUID BTWN 21Z MON AND 00Z TUE XCPT NW MOST CNTYS. TMPS CHALLENGING AS THE MODELS ARE TRYING TO FLOOD WARMER AIR IN AT THE SFC MUCH QUICKER THAN PREVIOUS FCST HAD. FOR NOW WILL GO WITH HIGHS NEAR FREEZING ACROSS THE NWRN MOST CNTYS (WHERE WEDGE ALWAYS HANGS ON THE LONGEST) TO BTWN 45-50 ALONG CSTL AREAS. DESPITE HOW MESSY MONDAY LOOKS...QPF FCST THRU 00Z TUE BEFORE THE CHANGEOVER TO LIQUID SUGGESTS THE EVENT WOULD FALL INTO A WINTER WEATHER ADVSRY HEADLINE VS WARNING HEADLINE. NO HEADLINES WILL BE ISSUED WITH THIS FCST GIVEN A FOURTH / FIFTH PERIOD EVENT. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... 12/12Z NUMERICAL MODELS DEPICT LOW PRESSURE TRACKING NE FROM THE DEEP SOUTH TO THE SRN APPALACHIANS MONDAY EVENING...THEN RAPIDLY DEEPENING AS IT LIFTS NE INTO THE MID-ATLANTIC REGION BY MIDDAY TUESDAY AS A VIGOROUS UPPER TROUGH DIGS ACROSS THE SRN/CENTRAL APPALACHIANS. THERMAL PROFILES SUGGEST MIXED PCPN COULD CONTINUE INTO THE EVENING OVER THE PIEDMONT. OVERNIGHT LOWS SHOULD OCCUR IN THE EVENING...WITH RISING TEMPERATURES OVERNIGHT AS THE LOW-LEVEL FLOW BECOMES SSE. COLDER TEMPERATURES WILL LIKELY PERSIST THE LONGEST IN THE FAR NW PIEDMONT COUNTIES WHERE SOME POCKETS OF -FZRA COULD CONTINUE OVERNIGHT...BUT GENERALLY ALL RAIN IS EXPECTED BY EARLY TUESDAY MORNING. PERIODS OF MODERATE RAIN ARE POSSIBLE LATE MONDAY NIGHT INTO TUESDAY AS A BAND OF STRONG VERTICAL ASCENT PASSES OVER THE REGION. STRONG PRESSURE FALLS COULD PRODUCE A MODESTLY STRONG SOUTHERLY WIND ACROSS THE ERN THIRD OF THE AREA FOR A 3-6HR PERIOD TUESDAY. TEMPERATURES WARM TO AT LEAST THE MID/UPPER 50S ACROSS THE ERN HALF OF THE AREA TUESDAY...WITH LOW 60S POSSIBLE ALONG THE COAST...WHILE THE PIEDMONT STRUGGLES TO RISE ABOVE THE UPPER 40S/LOW 50S. GENERALLY EXPECTING DRIER CONDITIONS BY TUESDAY NIGHT...ALTHOUGH SOME 20-30% POPS WILL LINGER ACROSS THE N AS A SECONDARY TROUGH SWINGS ACROSS THE NRN MID-ATLANTIC. DRY AND MILD WEDNESDAY UNDER WNW FLOW WITH HIGHS IN THE UPPER 40S TO MID 50S. A COLD FRONT TRACKS ACROSS THE AREA WEDNESDAY NIGHT...FOLLOWED BY CANADIAN HIGH PRESSURE THURSDAY. THIS SHOULD PUSH TEMPERATURES BELOW NORMAL...BUT WITHIN -1 ST DEV. A MODERATING TREND COMMENCES LATE WEEK AS HIGH PRESSURE MOVES OFFSHORE AND LOW PRESSURE TRACKS THROUGH THE GREAT LAKES. && .AVIATION /09Z SATURDAY THROUGH WEDNESDAY/... PLENTY OF CLOUDINESS ACROSS THE AREA AS LOW PRESSURE MOVES WELL OFFSHORE AND THE BASE OF AN UPPER TROUGH SWINGS ACROSS THE REGION. MODIFIED ARCTIC HIGH PRESSURE BUILDS INTO THE MIDWEST THE REST OF TONIGHT INTO SATURDAY WITH A MUCH COLDER AIRMASS FILTERING INTO THE MID ATLANTIC REGION DURING THIS TIME. TEMPERATURE AND PRESSURE GRADIENTS WILL RESULT IN NW WINDS BECOMING BREEZY FROM NW TO SE THE REST OF TONIGHT...BECOMING GUSTY AFTER 13/1100Z AND CONTINUING THROUGH THE REST OF SATURDAY. INLAND WINDS AVERAGING 15KT WITH GUSTS UP TO 20-25KT...ALONG THE COAST WINDS WILL AVERAGE 20-25KT WITH GUSTS UP TO 30-35KT. SKIES REMAIN MOSTLY CLOUDY AND THEN START TO BREAK UP AROUND SUNSET. SFC HIGH FINALLY BUILDS INTO THE REGION BY SUN MORNING...HOWEVER NW WINDS WILL BE SLOW TO DIMINISH OVERNIGHT (ESPECIALLY ALONG THE IMMEDIATE COAST) DUE TO A VERY GRADUAL RELAXING OF THE TEMP/PRESSURE GRADIENT. HIGH PRESSURE DOMINATES ON SUNDAY WITH DRY WX...GENERALLY LIGHT WINDS...AND VFR CONDITIONS. NEXT COMPLEX WEATHER SYSTEM BEGINS TO IMPACT THE AREA LATE SUNDAY NIGHT. PLENTY OF COLD AIR IN PLACE FOR PRECIP TO BEGIN AS ALL SNOW SUNDAY NIGHT INTO MONDAY MORNING. HOWEVER...A DEEPENING LOW MOVING IN FROM THE SW IS EXPECTED TO PULL WARMER AIR INTO THE REGION. THIS WILL COMPLICATE PRECIP FORECAST...ESPECIALLY ACROSS CNTRL VA WHERE COLDER AIR MAY LINGER AT THE SFC. COULD SEE A WINTRY MIX NORTHWEST HALF OF FA AND A CHANGEOVER TO ALL RAIN ACROSS THE SOUTHEAST. REGARDLESS OF PRECIP TYPE...EXPECT CIG/VIS REDUCTIONS ONCE PRECIP BEGINS SUNDAY NIGHT AND CONTINUING INTO TUESDAY. A BREAK IN PRECIP AND FLIGHT RESTRICTIONS IS ANTICIPATED TUESDAY NIGHT BUT COULD BE SHORT- LIVED. ANOTHER WEATHER DISTURBANCE MAY BRUSH ACROSS NRN VA AND THE MD LOWER EASTERN SHORE WEDNESDAY MORNING BUT IMPACTS ARE NOT ANTICIPATED AT LOCAL TAF SITES AT THE MOMENT. && .MARINE... 10 PM UPDATE...BEGAN MARINE HEADLINES WITH 10 PM ISSUANCE. SCA CONDITIONS TO BEGIN ACROSS NRN WATERS IN THE BALLPARK OF 400 AM... WITH WINDS INCREASING RAPIDLY TO GALE FORCE GUSTS FROM NORTH TO SOUTH AROUND SUNRISE. PREVIOUS DISCUSSION... LOW PRESSURE IS TRACKING ENE OFF THE NC COAST THIS AFTERNOON. MEANWHILE...ANOTHER AREA OF LOW PRESSURE IS TRACKING ACROSS THE ERN LAKES...WITH AN ARCTIC COLD FRONT TRAILING THROUGH THE OHIO VALLEY...AND ARCTIC HIGH PRESSURE SPILLING INTO THE UPPER MIDWEST. THE COASTAL LOW WILL BRING A PERIOD OF SN...WHICH WILL REDUCE VSBY LATE THIS AFTERNOON AND EVENING (MAINLY S). AS THE LOW LIFTS TO THE NE TONIGHT THE ARCTIC COLD FRONT WILL PASS ACROSS THE REGION WITH STRONG CAA DEVELOPING LATE TONIGHT...AND CONTINUING THROUGH SATURDAY INTO SATURDAY NIGHT AS THE ARCTIC HIGH BUILDS IN FROM THE NW. A NW WIND WILL AVERAGE 25-30KT WITH FREQUENT GUSTS OF 35-40KT OVER THE OCEAN AND BAY. SEAS BUILD TO 5-8FT WITH 4-5 FT WAVES IN THE BAY. GALE FLAGS CONTINUE FOR LATE TONIGHT THROUGH SATURDAY NIGHT. FOR THE RIVERS AND SOUND...WIND SPEEDS REMAIN CAPPED AT HIGH-END SCA AT THIS TIME. FREEZING SPRAY IS EXPECTED AS TEMPERATURES PLUMMET SATURDAY AND ESPECIALLY SATURDAY NIGHT/SUNDAY MORNING...WITH A FREEZING SPRAY ADVISORY IN EFFECT FOR SATURDAY NIGHT INTO SUNDAY MORNING. THE WIND WILL DIMINISH SUNDAY INTO SUNDAY NIGHT AS THE HIGH SETTLES ACROSS THE AREA. LOW PRESSURE APPROACHES FORM THE SW EARLY NEXT WEEK...AND TRACKS UP THE PIEDMONT TUESDAY. THIS WILL ALLOW FOR A MODESTLY STRONG SSE WIND AND BUILDING SEAS/WAVES. && .TIDES/COASTAL FLOODING... STRONG NW FLOW ASSOCIATED WITH AN ARCTIC COLD FRONT WILL PRODUCE BLOW-OUT TIDES / LOW WATER ADVISORIES FOR SOME AREAS EARLY SATURDAY MORNING...AND MUCH OF THE COASTLINES SATURDAY AFTERNOON AND NIGHT. THE MAIN AREAS EARLY SATURDAY MORNING THAT COULD HAVE LOW WATER ARE ALONG THE ATLANTIC COAST N OF CAPE CHARLES. A LOW WATER ADVISORY HAS BEEN ISSUED FROM 08-13Z (3 TO 8 AM). && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...WIND CHILL ADVISORY FROM MIDNIGHT TONIGHT TO 10 AM EST SUNDAY FOR MDZ021>025. NC...NONE. VA...WIND CHILL ADVISORY FROM MIDNIGHT TONIGHT TO 10 AM EST SUNDAY FOR VAZ075>078-085-099-521-522. MARINE...LOW WATER ADVISORY UNTIL 8 AM EST THIS MORNING FOR ANZ650-652- 654. FREEZING SPRAY ADVISORY FROM 7 AM THIS MORNING TO NOON EST SUNDAY FOR ANZ630>632-634-650-652-654-656. GALE WARNING UNTIL 10 AM EST SUNDAY FOR ANZ650-652-654. GALE WARNING UNTIL 7 PM EST THIS EVENING FOR ANZ656-658. FREEZING SPRAY ADVISORY FROM 7 PM THIS EVENING TO NOON EST SUNDAY FOR ANZ658. SMALL CRAFT ADVISORY UNTIL NOON EST SUNDAY FOR ANZ633-635>638. GALE WARNING UNTIL MIDNIGHT EST TONIGHT FOR ANZ630>632-634. && $$ SYNOPSIS...MPR NEAR TERM...MPR SHORT TERM...MPR/SAM LONG TERM...AJZ AVIATION...BMD MARINE...BMD TIDES/COASTAL FLOODING...AKQ

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