Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 161049 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 649 AM EDT THU APR 16 2015 .SYNOPSIS... A FRONTAL BOUNDARY WILL REMAIN STALLED ACROSS THE CAROLINAS INTO TONIGHT. WEAK WAVES OF LOW PRESSURE RIDING NORTHEAST ALONG THE FRONT WILL COMBINE WITH A STRONG WEDGE OF HIGH PRESSURE TO KEEP COOL AND DAMP CONDITIONS IN PLACE INTO EARLY FRIDAY. SLIGHTLY WARMER AIR RETURNS BY WEEKS END AHEAD OF ANOTHER COLD FRONT THAT WILL CROSS THE AREA EARLY IN THE WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... AS OF 255 AM EDT THURSDAY... CONTINUED PERSISTENCE FORECAST OVER THE NEXT 24 HOURS WITH THE LOW LEVEL WEDGE LOCKED IN PLACE AND ENHANCED BY PERIODIC ROUNDS OF LIGHT RAIN AS IMPULSES SLIDE ACROSS FROM THE RESIDUAL SYSTEM TO THE WEST. THIS SHOULD KEEP CLOUDS ACROSS MUCH OF THE REGION INTO TONIGHT WITH PERHAPS SOME BREAKS DEVELOPING OVER THE FAR WEST ALONG THE PERIPHERY OF THE COOL POOL TODAY...AND EAST OF HIGHWAY 29 WHERE DRIER AIR HAS ADVECTED IN FROM THE NE. SOME BREAKS COULD ALSO DEVELOP AT TIMES ELSEWHERE ESPCLY IF RAINFALL IS LESS GIVEN MORE MID DECK ATTM BUT IFFY. RAIN CHANCES ALSO TRICKY UNDER GRADUAL VEERING FLOW ALOFT OVER THE CAD AND WEAK ISENTROPIC LIFT INTO TONIGHT. LATEST GUIDANCE RATHER SPREAD OUT WITH SOME CONSENSUS TO FOCUS MORE ALONG A CORRIDOR FROM DAN-BCB-LWB THIS MORNING PER ONGOING UPPER DIFFLUENCE NORTH OF A PASSING JET MAX...AND ALONG THE SOUTHERN BLUE RIDGE GIVEN WEAK UPSLOPE INTO THE AFTERNOON. HOWEVER UNDERCUTTING BY DRY AIR TO THE NE LOOKS TO MAKE MOST RAIN/DRIZZLE SPOTTY...WITH LOW LEVEL CONVERGENCE PERHAPS SHIFTING BACK ACROSS THE FAR WEST LATER TODAY. THIS IN LINE WITH WHERE BETTER 85H WARM ADVECTION WILL EXIST ON THE WESTERN FLANK OF THE WEDGE AHEAD OF ANOTHER UPSTREAM IMPULSE. OVERALL THIS SPELLS MOSTLY CHANCE TO LOW LIKELY POPS AT TIMES ESPCLY CENTRAL SECTIONS FOR MAINLY LIGHT QPF TODAY WITH TEMPS ONLY RISING A CAT OR TWO NEAR THE BLUE RIDGE. HOWEVER COULD POSSIBLY TOP 60 EAST OF LYH-DAN...AND NEAR BLF WHERE GUSTY DOWNSLOPE SE FLOW WILL LINGER AND PRECIP MAY BECOME MORE SHOWERY LATER ON. WEDGE STARTS TO SLOWLY BREAK DOWN OVERNIGHT AS THE HIGH SWINGS FARTHER OFFSHORE BUT AGAIN THINK GUIDANCE TOO FAST TO ERODE WITH A TYPICAL INDUCED BUBBLE HIGH LIKELY STUCK NEAR THE BLUE RIDGE. THIS SHOULD AGAIN WITH LACK OF MUCH UPPER SUPPORT KEEP POPS MOSTLY IN THE LOW CHANCE RANGE EXCEPT PERHAPS FAR WEST/NW AHEAD OF PASSING SHORTWAVE ENERGY LIFTING BY TO THE NW LATE. OTRW APPEARS MORE CLOUDS/FOG AND SOME SPOTTY -DZ LIKELY AS WARMING ALOFT INCREASES WHICH SHOULD HOLD TEMPS UP CLOSER TO THE 45-53 RANGE FOR THE MOST PART. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... AS OF 335 AM EDT THURSDAY... HIGH PRESSURE WILL CONTINUE TO MOVE EAST INTO THE ATLANTIC OCEAN FRIDAY INTO SATURDAY. MEANWHILE...LOW PRESSURE LOCATED OFF THE SOUTH CAROLINA COAST FRIDAY MORNING WILL LIFT NORTHEAST ALONG THE EAST COAST. A COLD FRONT CROSSES THROUGH THE FORECAST AREA FRIDAY INTO FRIDAY NIGHT. WEDGE SHOULD BREAK DOWN/ERODE ON FRIDAY WITH SURFACE WINDS BECOME SOUTHWEST AHEAD OF THE FRONT DURING THE DAY. HIGH TEMPERATURES ON FRIDAY ARE A CHALLENGE...BECAUSE THEY ARE DEPENDENT ON WHEN...WHERE AND HOW FAST THE WEDGE ERODES. HIGH TEMPERATURES WILL RANGE FROM AROUND 60 DEGREES IN THE NORTHERN MOUNTAINS TO THE MID 70S IN THE SOUTHEAST. POPS ARE ALSO PROBLEMATIC ON FRIDAY. FIRST START FRIDAY MORNING WITH CHANCE OF RAIN...THEN CHANGE TO CONVECTIVE WITH FRONTAL BOUNDARY ROLLING THROUGH AREA. BELIEVE THERE IS ENOUGH INSTABILITY ON FRIDAY TO ADD MENTION OF THUNDERSTORMS. WEAK HIGH PRESSURE WILL BUILD EAST INTO OUR REGION FRIDAY NIGHT. LOW TEMPERATURES FRIDAY NIGHT WILL VARY FROM THE MID 40S IN THE MOUNTAINS TO THE MID 50S IN THE PIEDMONT. SURFACE HIGH PRESSURE BUILDS EAST INTO THE REGION SATURDAY. ALLOWED FOR FOR SOME SLIGHT TO CHANCE POPS SATURDAY AFTERNOON. HIGH TEMPERATURES SATURDAY WILL WARM INTO THE MID 60S IN THE MOUNTAINS THE UPPER 70S IN THE PIEDMONT. RAIN WILL SPREAD NORTHEAST INTO OUR REGION SATURDAY NIGHT INTO SUNDAY. LOW TEMPERATURES SATURDAY NIGHT WILL AVERAGE FROM AROUND 50 TO THE UPPER 50S. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... AS OF 345 AM EDT THURSDAY... 00Z GFS AND ECMWF AND THEIR ENSEMBLES HAD DECENT CONSENSUS FOR THE EXTENDED PERIOD. CENTRAL ROCKIES LOW OPENS AND LIFTS INTO THE UPPER MISSISSIPPI VALLEY SATURDAY NIGHT THROUGH MONDAY. THEN CLOSED LOW IN THE NORTHERN STREAM REMAINS OVER THE GREAT LAKES THROUGH WEDNESDAY. LOW PRESSURE OVER THE MISSISSIPPI VALLEY WILL BRING A WARM FRONT ACROSS THE MID ATLANTIC REGION SUNDAY NIGHT AND MONDAY. SURFACE PATTERN WILL BE MORE COMPLICATED. MODELS WERE SHOWING SOME INDICATIONS OF SURFACE BASED COLD AIR DAMMING. A TRIPLE POINT LOW DEVELOPS ON MONDAY OVER VIRGINIA THEN TRACKS TOWARD NEW JERSEY COAST. A SURGE OF COLDER AIR COMES IN ON WEDNESDAY. LIFT FROM THE SURFACE LOW CROSSING THE MID ATLANTIC STATES AND A PROLONGED PERIOD OF INFLOW OFF THE ATLANTIC WILL RESULT IN A HIGH PROBABILITY OF PRECIPITATION SUNDAY AND SUNDAY NIGHT. GIVEN CONSISTENCY OFF MODELS IN SHOWING THE THREAT FOR HEAVY RAIN ESPCLY ALONG THE BLUE RIDGE WILL MENTION IN THE HWO FOR LATE IN THE WEEKEND. && .AVIATION /12Z THURSDAY THROUGH MONDAY/... AS OF 630 AM EDT THURSDAY... RAIN/DRIZZLE CONTINUES TO INCREASE FROM SOUTH TO NORTH THIS MORNING...AIDED BY SE UPSLOPE FLOW AND DIFFLUENCE ALOFT. AT THE SAME TIME...HAVE SEEN HIGH PRESSURE WEDGE SOUTH ALONG THE EASTERN SLOPES OF THE BLUE RIDGE...PROVIDING A SURGE OF DRIER AIR INTO THE LOW LEVELS OF THE ATMOSPHERE FROM KROA TO KLYH WHERE SEEING MORE IN THE WAY OF MID DECK CIGS EARLY THIS MORNING. HOWEVER WITH MOISTURE/PRECIP AGAIN INCREASING...EXPECTING CIGS TO AGAIN DROP FROM CURRENT OVERALL VFR LEVELS BACK INTO MVFR FROM SOUTH TO NORTH THIS MORNING-EARLY AFTERNOON WITH LOCAL IFR CONDITIONS ALSO POSSIBLE ALONG THE BLUE RIDGE. PATCHY RAIN/DRIZZLE/FOG MAY ALSO BE ENOUGH TO LOWER VSBYS INTO MVFR LEVELS...BUT MOSTLY FROM KBCB/KROA SE TO KDAN AND DOWN ALONG THE BLUE RIDGE TO NEAR TNB. HIGH PRESSURE WILL REMAIN BANKED AGAINST THE APPALACHIANS THIS AFTERNOON...WITH WINDS BECOMING MORE SOUTHEASTERLY ALOFT BY LATE IN THE DAY. ADDED FAINT UPPER LEVEL ENERGY PASSING ACROSS THE AREA WILL SUPPORT CONTINUED PATCHY RAINFALL...AS WELL AS CAUSE CEILINGS TO GRADUALLY LOWER FURTHER DURING MID AFTERNOON AS EARLIER RAINFALL ADDS MOISTURE TO THE LOW LEVELS OF THE ATMOSPHERE. CONFIDENCE IN TIMING OF LOWER CIGS THOUGH REMAINS LOW GIVEN UNCERTAINTY IN THE DEGREE OF RAINFALL GIVEN SUCH WEAK FEATURES PASSING THROUGH THE WEDGE. THUS TRENDING TOWARD WIDESPREAD MVFR FROM MID AFTERNOON ONWARD BUT WITH ONLY SPOTTY PRECIP FOR NOW. LOW LEVEL WEDGE STARTS TO BREAK DOWN TONIGHT AS THE FLOW VEERS FROM SOUTHEAST TO MORE SOUTHERLY OVERNIGHT. THIS MAY ACTUALLY HELP MOISTEN THINGS FURTHER PROVIDING FOR OVERALL SUB-VFR AND RESIDUAL SPOTTY SHOWERS WITH POTENTIAL FOR MORE IN THE WAY OF LOW END IFR/LIFR IN STRATUS/FOG/DZ OVERNIGHT. EXTENDED AVIATION... ON FRIDAY...LOW LEVEL FLOW TURNS TO THE SOUTHWEST IN ADVANCE OF A COLD FRONT. ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS ARE POSSIBLE IN THE AFTERNOON...ESPECIALLY ONCE HIGH PRESSURE WEDGED AGAINST THE EASTERN FACE OF THE APPALACHIANS MOVES AWAY. A COLD FRONT WILL PASS ACROSS THE AREA FRIDAY NIGHT...WITH DRIER HIGH PRESSURE BUILDING IN BEHIND FOR SATURDAY. A COMPLEX STORM SYSTEM WILL BEGIN TO AFFECT THE REGION LATER IN THE WEEKEND WITH A WARM FRONT BRINGING WIDESPREAD MVFR/IFR CONDITIONS IN RAIN SUNDAY/SUNDAY NIGHT FOLLOWED BY ANOTHER COLD FRONTAL PASSAGE MONDAY. THIS LIKELY TO KEEP PERIODS OF MVFR IN PLACE UNTIL THE FRONT POSSIBLY CLEARS THE REGION LATER MONDAY. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH NEAR TERM...JH SHORT TERM...KK LONG TERM...AMS AVIATION...JH/NF

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