Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 190905 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 505 AM EDT SUN APR 19 2015 .SYNOPSIS... HIGH PRESSURE WAS OVER SOUTHEAST CANADA AND LOW PRESSURE WAS IN ARKANSAS WITH A WARM FROM EXTENDING INTO SOUTH CAROLINA. THE LOW AND WARM FRONT WILL MOVE NORTH TODAY AND TONIGHT. A COLD FRONT CROSSES THE REGION ON MONDAY THEN HIGH PRESSURE BUILDS IN FOR TUESDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 430 AM EDT SUNDAY... WARM FRONT ASSOCIATED WITH A LOW IN ARKANSAS WILL MOVE NORTH TODAY AND WILL CROSS THROUGH THE FORECAST AREA TONIGHT. STRONG SYNOPTIC SCALE LIFT WILL PRODUCE WIDESPREAD RAIN ACROSS THE FORECAST AREA. LOW LEVEL JET INCREASING TO 50-60 KNOTS FROM THE SOUTHEAST WILL RESULT IN STRONG UPSLOPE AND ISENTROPIC LIFT. RAIN WILL SPREAD INTO THE AREA FROM SOUTHWEST TO NORTHEAST BEFORE 18Z/2PM. MOST LOCATIONS WILL HAVE ABOUT A 12 HOUR PERIOD OF LIGHT TO MODERATE RAIN. HAVE PRECIPITATION ENDING FROM SOUTHWEST TO NORTHEAST AFTER 06Z/2AM. TEMPERATURES STARTING THE DAY QUITE MILD. GRIDDED LAMP GUIDANCE INDICATED STEADY AND POSSIBLY SLIGHTLY FALLING TEMPERATURES TODAY. LITTLE CHANGE IN AIR MASS IS EXPECTED TONIGHT WITH TEMPERATURES AND DEW POINTS REMAINING MAINLY IN THE 50S. THE STRONG WINDS THROUGH A DEEP LAYER WILL PROVIDE LARGE HELICITY VALUES LATE THIS AFTERNOON INTO THIS EVENING. THERE IS A LOW CHANCE THERE COULD BE ENHANCED DIRECTIONAL SHEAR AS THE WARM FRONT CROSSES. FOR NOW WILL LEAVE OUT ANY THUNDER. && .SHORT TERM /MONDAY THROUGH WEDNESDAY/... AS OF 345 AM EDT SUNDAY... THE NEW WEEK STARTS OFF WITH OUR REGION IN A WARM AND MOIST AIRMASS. AS TEMPERATURES RISE WELL INTO THE 70S ON MONDAY THE ATMOSPHERE WILL DESTABILIZE AHEAD OF THE APPROACHING COLD FRONT AND THUNDERSTORMS ARE EXPECTED TO DEVELOP. THE DYNAMIC ENVIRONMENT SUPPORTS THE CHANCE FOR SOME SEVERE STORMS AND THE SPC SLIGHT RISK LOOKS TO BE ON TARGET ACROSS OUR AREA WITH THE POTENTIAL FOR SVR WEATHER INCREASING EASTWARD WHERE INSTABILITY WILL BE GREATER. IT WILL ALSO BE QUITE BREEZY WITH EFFICIENT DOWNWARD MOMENTUM TRANSFER IN A WELL MIXED BOUNDARY LAYER. THE FRONT SHOULD BE CLEARING THE EASTERN ZONES EARLY MONDAY EVENING. COLDER AIR WORKING IN ON NW WINDS BEHIND THE FRONT WILL COMBINE WITH LOW LEVEL MOISTURE TO GENERATE SOME UPSLOPE SHOWERS ACROSS THE FAR WESTERN SLOPES MONDAY NIGHT. A BROAD CLOSED UPPER LOW BUILDING IN OVER THE NORTHEAST US WILL THEN KEEP COOL...BREEZY...AND UNSETTLED WEATHER CONDITIONS ACROSS THE REGION THROUGH MIDWEEK. TUESDAY LOOKS TO BE THE BEST CHANCE FOR A BREAK IN THE ACTION AS ANY LINGERING SHOWERS ACROSS THE FAR WEST DISSIPATE BY EARLY MORNING. BY WEDNESDAY THE NEXT COLD FRONT WILL BE ROTATING IN FROM THE WEST WITH A CHANCE FOR SHOWERS AND MAYBE SOME THUNDER ESPECIALLY WEST OF THE BLUE RIDGE. TEMPERATURES TUESDAY AND WEDNESDAY WILL BE RUNNING AT OR SLIGHTLY BELOW NORMAL WITH UPPER 50S/LOWER 60S WEST OF THE BLUE RIDGE AND MID 60S TO AROUND 70 EAST. && .LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/... AS OF 350 PM EDT SATURDAY... MODELS IN BETTER AGREEMENT TODAY ON A DEEP AND BROAD UPPER LOW CENTERED ACROSS THE EASTERN GREAT LAKES DOMINATING THE WEATHER THROUGH MOST OF THE REMAINDER OF THE WORK WEEK. THIS WILL LEAVE UNSETTLED CONDITIONS ACROSS THE MOUNTAINS...SOMEWHAT LESS SO ACROSS THE PIEDMONT. FOLLOWING THIS DISTURBANCE COMES THE BONAFIDE COLDER AIR WHICH PROMISES TO PUSH 850MB TEMPS DOWN TO 0C OR BELOW FOR MUCH OF THE REMAINDER OF THE WEEK ACROSS THE NORTHERN AREAS. THE UPPER TROUGH GRADUALLY SHIFTS MORE TOWARD THE MID-ATLANTIC LATE IN THE PERIOD...STRENGTHENING THE NORTHWEST FLOW ACROSS THE REGION...AND ALLOWING 850MB TEMPS TO BOTTOM OUT ACROSS THE NORTH AROUND -5C BY SATURDAY. THIS PATTERN WILL CONTINUE TO RESULT IN A SIGNIFICANT TEMPERATURE DIFFERENCE FROM THE WESTERN MOUNTAINS WITH CLOUDS AND VARIABLE CLOUDS/SCATTERED SHOWERS AND MORE SUNNY/DOWNSLOPE NORTHWEST FLOW ACROSS THE PIEDMONT. OVERALL...TEMPERATURES SHOULD AVERAGE BELOW NORMAL THROUGH THE PERIOD...PERHAPS MUCH BELOW IN THE WEST. MEXMOS SHOWS SEVERAL DAYS WITH HIGHS ONLY IN THE 50S/60S WEST AND LOWS IN THE UPPER 30S TO LOWER 40S. WIND AND CLOUDS SHOULD PREVENT ANY FROST/FREEZE CONCERN AT THIS POINT. && .AVIATION /09Z SUNDAY THROUGH THURSDAY/... AS OF 145 AM EDT SUNDAY... MODELS CONTINUE TO BE CONSISTENT WITH CLOUDS AND THEN RAIN WILL SPREAD INTO THE AREA FROM SOUTHWEST TO NORTHEAST TONIGHT. EXPECT CEILINGS TO LOWER TO MVFR ON THE 09Z/5AM-16Z/11AM TIME RANGE. A STRONG SOUTHEAST LOW LEVEL JET WILL DEVELOP JUST AFTER MIDNIGHT WHICH MAY BRING WIND GUSTS TO 30 KTS TODAY. WITH A WEDGE OF HIGH PRESSURE IN PLACE ALONG AND EAST OF THE BLUE RIDGE...AFTER SUNSET THESE STRONG WINDS ARE NOT EXPECTED TO REACH THE SURFACE. HAVE LLWS IN THE KDAN...KLWB AND KBCB TAFS AFTER 00Z/8PM. A STRONG UPSLOPE FLOW WILL TRANSPORT ABUNDANT MOISTURE INTO THE REGION NORTH OF A STATIONARY FRONT TODAY. CEILINGS WILL LOWER TO IFR LATE THIS AFTERNOON INTO THE EVENING AND WILL REMAIN LOW OVERNIGHT. EXTENDED AVIATION... A COLD FRONT APPROACHES LATER MONDAY WITH SOME STORMS POSSIBLE AHEAD OF AND ALONG THE FRONT...ESPECIALLY EAST OF THE BLUE RIDGE. THIS IS LIKELY TO KEEP PERIODS OF MVFR AND BRIEF IFR IN STORMS UNTIL THE FRONT CLEARS THE REGION MONDAY EVENING. VFR RETURNS LATER MONDAY NIGHT AND TUESDAY WITH HIGH PRESSURE BUILDING IN BEHIND THE FRONT WITH A DRIER AIRMASS. THEN THE NEXT CHANCE OF MVFR CONDITIONS AND PRECIPITATION WILL BE IN THE MOUNTAINS ON WEDNESDAY AND THURSDAY. && .HYDROLOGY... AS OF 430 AM EDT SUNDAY... HAVE EXPANDED THE FLOOD WATCH FOR MORE OF THE SOUTHERN BLUE RIDGE AND FOR THE BLUE RIDGE AND ADJACENT EASTERN COUNTIES NORTH OF OF ROANOKE. BUFKIT SOUNDINGS SHOWED A DEEP LAYER FROM THE SURFACE THROUGH MID LEVELS OF THE ATMOSPHERE WITH SOUTHEAST WINDS...THAT WILL BE INCREASING TO AROUND 50 KNOTS THIS AFTERNOON AND EVENING. PRECIPITABLE WATER VALUES JUST ABOVE 1.5 INCHES WILL BE ADVECTED INTO THE FORECAST AREA. THE STRONGEST LIFT AND HIGHEST RAINFALL AMOUNTS WILL BE FROM 18Z/2PM THROUGH 06Z/2AM SO HAVE ADDED HEAVY RAIN TO THE FORECAST ALONG THE BLUE RIDGE FOR THIS TIME FRAME. TOTAL RAINFALL AMOUNTS WILL RANGE FROM 1 TO 3 INCHES THROUGH 12Z/8AM MONDAY. FLASH FLOOD GUIDANCE VALUES WERE ROUGHLY 1.5 TO 2.5 INCHES FOR 3 HOURS. SO THIS AMOUNT OF RAINFALL HAS THE POTENTIAL TO PRODUCE FLOODING ON SMALL STREAMS AND CREEKS. PROBABILISTIC GUIDANCE FOR MAINSTEM RIVERS SUGGESTS A SMALL POSSIBILITY FOR MINOR FLOODING ALONG THE DAN RIVER AND NEW RIVER. HOWEVER...THE IS HIGHLY DEPENDENT ON THE AMOUNT OF RAINFALL THROUGH MONDAY MORNING. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...FLOOD WATCH THROUGH THIS EVENING FOR VAZ009-012>017-032. FLOOD WATCH FROM 2 PM EDT THIS AFTERNOON THROUGH LATE TONIGHT FOR VAZ022>024-033>035. NC...FLOOD WATCH THROUGH THIS EVENING FOR NCZ001>003-018>020. WV...NONE. && $$ SYNOPSIS...AMS NEAR TERM...AMS SHORT TERM...MBS LONG TERM...RAB AVIATION...AMS/PC HYDROLOGY...AMS

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