Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 211808 AFDRLX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON WV 154 PM EDT SUN SEP 21 2014 .SYNOPSIS...
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A COLD FRONT CROSSES THIS AFTERNOON. HIGH PRESSURE BUILDS IN MONDAY NIGHT...AND DOMINATES OUR WEATHER THROUGH THE REMAINDER OF THE WEEK WITH WARM DAYS AND COOL NIGHTS.
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&& .NEAR TERM /THROUGH TONIGHT/... 1000 AM UPDATE... LINE HAS DEVELOPED AND IS MOVING THROUGH THE EASTERN CWA...BUT WITH LITTLE FANFARE. UPDATED THE POPS TO REFLECT THIS AND CURRENTLY AWAITING THE COLD FRONT AND THE CONVECTION FIRE WITH THE MAIN BOUNDARY. PREV DISC... CONVECTION AHEAD OF A COLD FRONT CROSSING IN AND IL EARLY THIS MORNING STRUGGLING TO PUSH E AS INITIAL S/W TROUGH LIFTS OUT. AS A RESULT...CONVECTION HAS BECOME INCREASINGLY CONFINED TO AN AXIS JUST AHEAD OF THE FRONT. AS A RESULT...SHOWERS DO NOT REACH THE UPSTREAM /W/ EDGE OF THE FCST AREA UNTIL CLOSE TO DAYBREAK. MODELS ESPECIALLY NEAR TERM MODELS INSIST THE PRECIPITATION MOVES QUICKLY E ACROSS FCST AREA TODAY IN RESPONSE TO SECOND S/W TROUGH WHICH ALSO LIFTS OUT THIS MORNING...SO THIS PRECIPITATION MAY AGAIN STRUGGLE TO HOLD TOGETHER. POPS EVENTUALLY COME CLOSER IN LINE WITH PREV FCST AS FRONT AND WHATEVER DIURNAL HEATING WE CAN ACHIEVE CONVERGE ON THE FCST AREA THIS AFTERNOON BENEATH DIFFLUENT UPPER LEVEL FLOW AND FALLING HEIGHTS. SO NAM DYNAMICS SUGGEST AT LEAST TWO BANDS OF CONVECTION SWEEPING ACROSS WHILE WRFARW FOR EXAMPLE SUGGESTS SEVERAL. SEP HEATING AND CLOUD COVER EARLY ON WILL LIMIT INSTABILITY BUT CYCLONIC FLOW ALOFT HELPS PUSH MID LEVEL /H85-H7/ LAPSE RATES TO 6-7C/KM. FLOW IS ALSO MARGINAL WITH 30 KTS AT H85 AND 40 KTS MID LEVEL MEAN AND 60 KTS AT H5. WILL BE DIFFICULT BUT NOT IMPOSSIBLE TO CONVERT THIS TO DAMAGING WIND AT THE SFC BUT ISOLATED STRONGER GUSTS ARE POSSIBLE. THINK ANY DAMAGE IS MINOR AND ISOLATED ENOUGH FOR NO MENTION IN HWO AND NEAR TERM FCST. H7-H5 LAPSE RATES ARE LOWER OWING TO A STABLE LEVEL THERE SO HAIL IS NOT LIKELY DESPITE FREEZING LEVELS AS LOW AS 10 KFT AGL AND THE 60 KTS AT H5 WILL BE HARD TO TAP. SPC KEEPS PROBABILITIES AT 5 PERCENT ON BOTH IN A SEE TEXT. BRIEF CLEARING TAKES PLACE LATE TODAY AND TONIGHT IN THE WAKE OF THE FRONT...BUT CLOUDS INCREASE AGAIN OVERNIGHT IN THE CYCLONIC LOW LEVEL FLOW BENEATH THE POST FRONTAL INVERSION. CLOUD AND FLOW SHOULD PRECLUDE DENSE FOG TONIGHT ALTHOUGH SOME POST RAIN MIST AND LIMITED VALLEY FOG ARE LIKELY. MET AND MAV WERE A LITTLE HIGHER THAN PREV FCST ON TEMPERATURES BUT MADE JUST S SLIGHT MOVE IN THAT DIRECTION. THE TIMING ON HIGHS WILL VARY BASED ON THE MOVEMENT OF THE FRONT...BASICALLY EARLY E AND LATE W BUT DETAIL DIFFICULT TO CODE. MOVED TOWARD HIGHER GUIDANCE TONIGHT WITH THE TYPICAL SLOWER PUSH OF COOLER AIR TOWARD THE MOUNTAINS. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
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A VERY TRANQUIL AND DRY WEATHER PATTERN IS INDICATED BY ALL THE MODELS...WHICH IS EXPECTED AT THIS CLIMATOLOGICALLY DRIEST TIME OF THE YEAR. HIGH PRESSURE AT THE SURFACE AND ALOFT WILL DOMINATE THE REGION. THERE WILL BE PLENTY OF SUNSHINE EACH DAY AND MOSTLY CLEAR SKIES AT NIGHT. THE COMBINATION OF MOSTLY CLEAR SKIES AND DRY AIR WILL LEAD TO CHILLY TEMPERATURES MONDAY NIGHT...AND SOME NORTHERN MOUNTAIN VALLEY FROST EARLY TUESDAY MORNING CANNOT BE RULED OUT. OTHERWISE...EXPECT A WIDE RANGE IN DIURNAL TEMPERATURES WITH HIGHS GENERALLY IN THE LOWER TO MID 70S AND LOWS IN THE 40S FOR THE LOW LANDS. LEANING ON THE WARMER SIDE OF GUIDANCE BY DAY AND LOWER SIDE BY NIGHT.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
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SURFACE HIGH PRESSURE WILL SLIDE TO THE EAST COAST BY THURSDAY AND ALLOW A MODEST INCREASE OF LOW LEVEL MOISTURE FROM THE EAST AND SOUTHEAST THROUGH SUNDAY. HOWEVER...UPPER RIDGING ALOFT WILL HOLD. SO WHILE SOME LOW LEVEL MOISTURE WILL RETURN AS TIME GOES ON...THE PROSPECTS OF ANY RAIN ARE VERY LOW AT BEST. THE LOW LEVEL MOISTURE BANKING UP AGAINST EAST FACING SLOPES OF THE MOUNTAINS WILL ONLY BRING INCREASED CLOUDS BY THE WEEKEND. OTHERWISE...SUNSHINE WILL DOMINATE WEST OF THE MOUNTAINS. THERE WILL BE A SLOW WARMING TREND WITH HIGHS TO AROUND 80 BY THE WEEKEND AND LOWS GENERALLY IN THE 50S IN THE LOW LANDS.
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&& .AVIATION /18Z SUNDAY THROUGH FRIDAY/...
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LACKING SOME CONFIDENCE IN THE AVIATION FORECAST TODAY. COLD FRONT TO THE NORTHWEST WILL BE A QUICK MOVER THROUGH THIS AFTERNOON...DRIVEN BY A STRONG UPPER LEVEL TROUGH AXIS. A LINE OF CONVECTION IS CURRENTLY FORMING WITH THIS COLD FRONT WHICH DOMINATES THE FIRST 6 HOURS OF THE FORECAST. THE NORTHERN TERMINALS WILL HAVE THE BETTER CHANCE FOR THUNDERSTORMS...WHICH WILL BE CAPABLE OF SOME GUSTY WINDS THAT ARE ALREADY INCREASING AHEAD OF THE SYSTEM. ALSO INCLUDE BKW/MOUNTAINS IN THE BETTER TSRA THREAT. HAVE TEMPO GROUPS FOR SHRA ONLY AT HTS AND CRW. THE FRONT ITSELF IS LOOKING A LITTLE RAGGED...SO THE COVERAGE OF THE SHOWERS AND STORMS IS QUESTIONABLE AT THE TIME OF THIS FORECAST. THIS IS THE REASON FOR THE TEMPOS INSTEAD OF THE PREVAILING CONDITIONS IN THE TAFS. WIND SHIFTS TO THE NORTHWEST BEHIND THE FRONT...WITH WIND SPEEDS COMING DOWN BELOW 10KTS TONIGHT. EXPECT MVFR CEILINGS TO PERSIST BEHIND THE FRONT IN THE ADVECTION OF LOW LEVEL MOISTURE INTO THE AREA BEHIND THE FRONT. OPTED AGAINST FOG GIVEN THE CLOUDS AND PRESSURE GRADIENT WINDS STAYING AROUND 5KTS. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z MONDAY... FORECAST CONFIDENCE: MEDIUM. ALTERNATE SCENARIOS: TIMING AND COVERAGE OF CONVECTION MAY VARY. EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY OF WFO FORECAST TO AVAILABLE MODEL INFORMATION: H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS. L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. UTC 1HRLY 18 19 20 21 22 23 00 01 02 03 04 05 EDT 1HRLY 14 15 16 17 18 19 20 21 22 23 00 01 CRW CONSISTENCY H H H H H H H M H H H M HTS CONSISTENCY H H H H M H H H M M M M BKW CONSISTENCY M M M H H M M M M M M M EKN CONSISTENCY M M M M M M M M M M M M PKB CONSISTENCY M H H H H H H M H M M M CKB CONSISTENCY H M H H H M M M M H H M AFTER 18Z MONDAY... IFR STRATUS POSSIBLE MON MORNING...ESPECIALLY IN THE MOUNTAINS. IFR VALLEY FOG POSSIBLE TUE MORNING...ESPECIALLY ALONG RIVERS AND IN BETTER SHELTERED VALLEYS.
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&& .RLX WATCHES/WARNINGS/ADVISORIES... WV...NONE. OH...NONE. KY...NONE. VA...NONE. && $$ SYNOPSIS...TRM/JMV/SL NEAR TERM...TRM/26 SHORT TERM...JMV LONG TERM...JMV AVIATION...26

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