Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 300126 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 926 PM EDT FRI MAY 29 2015 .SYNOPSIS...
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HIGH PRESSURE WILL PERSIST OFFSHORE THROUGH SATURDAY WITH CONTINUED WARM AND HUMID CONDITIONS TO THE MID-ATLANTIC. A COLD FRONT WILL ENTER THE REGION LATE SUNDAY AND STALL OVER THE REGION INTO TUESDAY. HIGH PRESSURE IS EXPECTED TO SLIDE INTO THE REGION FOR THE MIDDLE PART OF NEXT WEEK.
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&& .NEAR TERM /THROUGH TONIGHT/...
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CONVECTIVE ACTIVITY WANING WITH SUNSET. IT WAS YET ANOTHER AFTERNOON/EVENING OF POPUP SHOWER/THUNDERSTORM ACTIVITY WITH A WARM AND MOIST ATMOSPHERE FROM HIGH PRESSURE OFF THE MID-ATLANTIC COAST. ANOTHER WARM NGT ON TAP FOR THE AREA. LOWS TNGT GNRLY IN M60S..L70S IN THE CITIES.
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&& .SHORT TERM /SATURDAY/... AREA RMNS IN THE SAME AIR MASS SAT - CD FNT RMNS TO OUR NW BUT IS WORKING ITS WAY IN THIS DIRECTION. BEST CHC OF TSTMS WL BE IN THE AFTN IN THE WRN PART OF THE CWA. HIGHS WL AGN BE IN THE MU80S. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... ON SATURDAY NIGHT...THE UPPER LEVEL RIDGE OFFSHORE WILL BEGIN TO BE SUPPRESSED BY A SHORTWAVE TROUGH PUSHING THROUGH CANADA. A COLD FRONT WILL BE APPROACHING FROM THE NW...EXTENDING DOWN THE ST LAWRENCE VALLEY INTO THE SOUTHER GREAT LAKES. AFTER ANY DIURNAL CONVECTION SUBSIDES...A CHANCE OF SHOWERS WILL REMAIN NEAR THE PA BORDER FOR ANY ACTIVITY THAT RACES AHEAD OF THE FRONT. OTHERWISE JUST ANOTHER MUGGY NIGHT WITH INCREASING CLOUDS AND LOWS IN THE 60S...LOWER 70S URBAN AREAS. CONFIDENCE IN THE SUNDAY TO SUNDAY NIGHT PERIOD IS NOT PARTICULARLY HIGH AS THE COLD FRONT ADVANCES INTO THE AREA. THERE IS STILL SOME MODEL SPREAD IN HOW QUICKLY THE FRONT WILL PUSH SOUTHWARD...BUT THE OVERALL TREND HAS BEEN SLOWER. THIS MAKES SENSE BECAUSE THE FRONT WILL BECOME PARALLEL TO THE UPPER FLOW AS IT PUSHES INTO THE STRONG RIDGE. A WAVE OF LOW PRESSURE WILL ALSO MOVE ALONG THE FRONT SOMETIME IN THIS TIME PERIOD. THUNDERSTORMS SEEM LIKE A GOOD BET...BUT WILL NOT BE GOING HIGHER THAN LIKELY YET DUE TO THE TIMING UNCERTAINTY. THIS ALSO MEANS HIGH TEMPS SUNDAY WILL LIKELY BE A BIT HIGHER...AND COULD ONCE AGAIN APPROACH 90 OVER THE SE CWA WHICH WILL HAVE FAIRLY LOW PRECIP CHANCES DURING MUCH OF THE DAY. IT LOOKS LIKE ANY SEVERE POTENTIAL SUNDAY WILL BE LIMITED AND TIED TO BUILDING INSTBY AS SHEAR WILL NOT BE PARTICULARLY STRONG. A BIGGER THREAT MAY BE DUE TO HEAVY RAIN AND FLOODING DUE TO THE STALLING FRONT...DEVELOPING LLJ SUNDAY NIGHT...AND FAVORABLE UPPER DIVERGENCE IN A HIGH PWAT ENVIRONMENT. HOWEVER...A LITTLE DIFFICULT TO SAY WHICH TIME PERIOD AND WHICH PART OF THE MID-ATLANTIC WOULD HAVE THE BIGGEST THREAT AT THIS TIME. A BIG SHIFT IN THE PATTERN WILL OCCUR BEHIND A COLD FRONT EARLY NEXT WEEK. AS THE FRONT DROPS SLOWLY SOUTH...RAIN CHANCES WILL SLOWLY DIMINISH MONDAY INTO TUESDAY. MEANWHILE...HIGH PRESSURE WILL BUILD OVER NEW ENGLAND SETTING UP A COOL AIR DAMMING WEDGE ACROSS THE REGION. TEMPERATURES WILL SHIFT FROM HEAT AND HUMIDITY MORE TYPICAL OF MID-JULY TO TEMPERATURES MORE TYPICAL OF MID-APRIL. AS THE HIGH GRADUALLY SHIFTS TO THE EAST AND WEAKENS...TEMPERATURES WILL GRADUALLY REBOUND TO NEAR NORMAL LEVELS BY THE END OF THE WEEK. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
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ISOLATED SHOWERS REST OF THE EVENING IN THE DC METROS. FOG PSBL LATE TNGT AT CHO/IAD/MRB. THERE WL BE CHCS FOR TSTMS AGN SAT AFTN...BEST CHC AT MRB. TIMING OF COLD FRONT SUNDAY-SUNDAY NIGHT A BIT SLOWER...BUT THUNDERSTORMS WILL STILL BE LIKELY AT SOME POINT DURING THE TIME PERIOD. HEAVY RAIN POSSIBLE...SO IFR FLIGHT CONDITIONS MORE LIKELY THAN THEY HAVE BEEN WITH RECENT SCATTERED STORMS. NELY FLOW 10 KT OR SO MON-TUE. SUB-VFR PSBL IN LOW CIGS/-RA.
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&& .MARINE...
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SLY FLOW 10 TO 15 KT CONTINUES TONIGHT UP THE MAIN PORTION OF THE BAY WITH HIGH PRESSURE OFF THE COAST. FLOW INCREASES SAT AHD OF A CD FNT. SCA FOR ALL BUT MIDDLE AND UPPER TIDAL POTOMAC SATURDAY AFTERNOON INTO THE OVERNIGHT. WINDS WILL DECREASE SOME SATURDAY NIGHT AND WILL KEEP SCA IN PLACE AS ORIGINALLY ISSUED...WHICH WILL BE IN EFFECT FOR THE MAIN CHANNEL OF THE BAY THROUGH THE NIGHT. SOUTHERLY FLOW ON SUNDAY MAY APPROACH SCA CONDITIONS BUT WILL BE MARGINAL. COLD FRONT PASSAGE APPEARS IT WILL BE A BIT SLOWER...BUT THUNDERSTORMS WILL STILL EVENTUALLY BECOME LIKELY SUNDAY AFTERNOON/NIGHT AND POSE A LOCALIZED WIND THREAT. GRADIENT WIND FIELD UNCERTAIN BY SUNDAY NIGHT AND WILL DEPEND ON FRONTAL POSITION. HIGH PRESSURE BUILDING IN BEHIND A COLD FRONT WILL LIKELY PUSH NORTHEASTERLY WINDS TO SMALL CRAFT ADVISORY LEVELS MONDAY INTO TUESDAY.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM NOON SATURDAY TO 2 AM EDT SUNDAY FOR ANZ530-537>542. SMALL CRAFT ADVISORY FROM 10 AM SATURDAY TO 8 AM EDT SUNDAY FOR ANZ531>534-543. && $$ UPDATE...JACKSON PREVIOUS...WOODY!/ADS/DFH

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