Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 201925 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 325 PM EDT MON APR 20 2015 .SYNOPSIS...
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A WARM FRONT RESIDES JUST NORTH OF THE AREA LATE TODAY. A COLD FRONT WILL PUSH EAST ACROSS THE REGION EARLY THIS EVENING. AN UPPER LOW WILL THEN PERSIST ACROSS THE GREAT LAKES TO NEW ENGLAND THROUGHOUT THE WEEK.
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&& .NEAR TERM /THROUGH TUESDAY/...
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SFC WMFNT HAS JUST SNUCK OVER THE MD/PA BORDER. CDFNT STILL ACROSS WVA. ALTHO CWFA W/IN WARM SECTOR...A CPL OF CHALLENGES HAVE CROPPED UP. FIRST IS THE DEBRIS CI WHICH HAS IMPEDED SGFNT WARMING. SECOND ARE MID LVL CAPS AT H8 AND H6. THE COMBO OF THE TWO HV RESULTED IN A COLUMN THAT STILL IS STBL. INITIATION HAS OCCURRED W OF THE CWFA... IN A MORE FVRBL ENVIRONMENT. TREND IN SOME GDNC IS TO DELAY ONSET OF PCPN. THE GDNC SETS THAT HAVENT CAUGHT ONTO THIS TREND HV BEEN DVLPG PCPN TOO SOON...AND HV BEEN NEGLECTED. BELIEVE THAT MID LVL COOLING WL STILL TAKE PLACE... AND THE CI SOON TO DEPART. THEREFORE...STILL BELIEVE THAT WE WL BE DSTBLZG SOON. DECENT SHEAR AND INCRSG INSTBY SUGGESTS THAT A THREAT FOR SVR WX STILL EXISTS. FURTHER...AS UPR LVL SPD MAX CREEPS UP COAST JUST AHD OF APPRCHG CDFNT...WL HV NCSRY FORCING FOR ENHANCED LIFT. THEREFORE WL HV DELAYED ONSET...OTRW HV MADE FEW CHGS TO GOING FCST TAFTN- EVNG. AS NAM DEPICTS...ONCE INITIATION BEGINS XPCT RAPID DVLPMNT TO TAKE PLACE. THINK ITLL BE MIXED MODE...W/ WIND AND HAIL THREATS. FZL AND WBZ QUITE LOW WHILE LOW-MID LVL LAPSE RATES MDT-HIGH. IN ADDITION...HV BACKED LLVL FLOW NEAR WMFNT. AS A RESULT...SPC HAS ISSUED A TOR WATCH FOR ENTIRE AREA TIL 02Z. WL HV DECREASING THUNDER CHCS AFTR SUNSET...BUT PCPN MAY LINGER TIL MIDNGT-ISH WHEN CDFNT CLEARS AREA. AFTER THAT LOOK FOR A RAPIDLY DRYING AMS AS WLY WINDS INCREASE. HV HELD ONTO SOME CLDS THO DUE TO MID LVL TROF AXIS. DP UPR LOW WL RESIDE NORTH OF THE GRTLKS TMRW...WHICH WL PROVIDE FAST MID-LVL FLOW. KEEPING A DRY FCST W/ CLDY PERIODS AS IMPULSES ZIP THRU THE FLOW. DOWNSLOPING WL PROVIDE THE WARMING IN SPITE OF CAA.
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&& .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
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NOT MUCH OF A BREAK BETWEEN SYSTEMS AS THE MID-ATLC STAYS JUST ON THE OUTER FRINGE OF A LARGE UPPER GREAT LAKES TROUGH. ONE OF THE WEAKER VORTS SLIDING AROUND THE BASE OF THE TROUGH WILL SLIDE INTO THE WINDWARD SIDE OF THE APLCNS LATE TUE NIGHT. LITTLE MORE THAN COOLER AIR WILL MAKE IT OVER THE MTNS...W/ THE MOISTURE DISSIPATING OVER THE HIGHER TERRAIN. HEADING INTO EARLY WED...A STRONGER LOW PRESSURE SYSTEM WILL BE DEVELOPING WELL TO OUR NORTH WHICH WILL ALSO STRENGTHEN THE INCOMING COLD FRONT. GUSTY SW WINDS WILL ARRIVE BEFORE ANY PRECIP E OF THE APLCNS...AND GRADUALLY PULL UP OUR COOL TEMPS FROM OVERNIGHT BACK INTO A WARMER REGIME BY MIDDAY. UNLIKE TODAY`S CONDITIONS...THIS FRONTAL PASSAGE IS NOT EXPECTED TO MUSTER UP MUCH INSTABILITY. THE SRN HALF OF THE CWA MAY SEE SOME WEAK CONVECTIVE POTENTIAL BUT THE REMAINDER OF THE AREA WILL SEE AT SOLID CHANCE FOR RAIN SHOWERS. TEMPS WILL BE ABOVE AVG FOR THE VA/MD PIEDMONT. QPF FAIRLY LIGHT FOR THIS PASSAGE AND A RELATIVELY BRIEF PERIOD OF THE MID AFTN TO EVE. BY LATE EVE...MOST OF THE PRECIP WILL BE SLIDING OUT OF THE SE PORTION OF THE CWA AND CLOUDS WILL ALLOW EXIT OFF THE COAST.
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&& .LONG TERM /THURSDAY THROUGH MONDAY/...
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LONG TERM PERIOD WILL BE DOMINATED BY A COLD UPPER-LEVEL LOW PRESSURE SYSTEM STALLED OVER THE NORTHEASTERN CONUS...WITH PERSISTENT CHILLY WEST OR NORTHWEST FLOW OVER THE REGION. A TROUGH MAY BRING PRECIPITATION TO THE AREA SATURDAY...BUT OTHER THAN THAT IT LOOKS MAINLY DRY. TEMPERATURES WILL BE WELL BELOW NORMAL /I.E. 10-15 DEGREES BELOW NORMAL/ THROUGH THE PERIOD WITH HIGH STRUGGLING TO GET OUT OF THE 50S AND LOWS IN THE UPPER 30S TO 40S.
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&& .AVIATION /19Z MONDAY THROUGH SATURDAY/...
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AM KEEPING VFR TAFS THRU THE PD. HWVR...THERE ARE OTHER CONSIDERATIONS. NMRS TSRA WL BE DVLPG TAFTN. XPCT BRIEF CIG/VIS RESTRICTIONS W/IN ANY STORMS. THE MITIGATING FACTOR IS AREAL CVRG. ONCE THAT BECOME CLEAR...THEN RESTRICTIONS WL BE ADDED TO TAFS. THREAT WINDOW WL BE 20/21Z THRU 02Z. WLY WINDS OVNGT THRU TUE...W/ GUSTS UP TO 20 KT ATTM. ANOTHER COLD FRONT WILL SWING THRU ON WED AFTN. GUSTY SW WINDS AHEAD OF THE FRONT AND MAINLY BRIEF/SCTD SHOWER ALONG THE BOUNDARY AS IT SLIDE THRU DURING THE 2ND HALF OF THE DAY. WLY FLOW 10 KT OR SO W/ MAINLY VFR EXPECTED THU-SAT.
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&& .MARINE...
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SLY FLOW TAFTN-EVE...SCA AT TIMES. STORMS POSSIBLE LATE AFTERNOON/EVENING WITH STRONG WINDS AND HAIL. COLD FRONT CROSSES TONIGHT WITH WIND SHIFT TO WEST. PERHAPS A WEAKENING OF WINDS NEAR DAWN TUESDAY...BUT THEN INCREASE AGAIN TO SCA LEVELS DURING THE DAY. SOLID SCA WINDS POSSIBLE ON WED AHEAD OF AND ALONG A COLD FRONT THAT IS EXPECTED TO SWING THRU THE WATERS BY LATE EVE. SCA GUSTS POSSIBLE IN WLY SURGE BEHIND FRONTAL BOUNDARY THURSDAY...THEN LIGHTER FLOW BELOW SCA CRITERIA LIKELY FRIDAY- SATURDAY.
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&& .TIDES/COASTAL FLOODING...
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WATER LEVELS STILL BETWEEN 1.5 AND 2.0 FT ABV ASTRO NORMS. AT THIS RATE...WILL HAVE MINOR FLOODING AT ANNAPOLIS AND BALTIMORE. SLY FLOW WILL REINFORCE THE POSITIVE DEPARTURES. HOWEVER...A COLD FRONT WILL BE APPROACHING...SWINGING AROUND WIND DIRECTION RIGHT NEAR THE TIME OF HIGH TIDE. THAT MAKES IT LOWER CONFIDENCE...BUT STILL OPTED TO ISSUE ADVY. WILL CONTINUE TO MONITOR.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...COASTAL FLOOD ADVISORY UNTIL 11 PM EDT THIS EVENING FOR MDZ011- 014. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT TUESDAY FOR ANZ530>534- 537>543. SMALL CRAFT ADVISORY UNTIL 1 AM EDT TUESDAY FOR ANZ535-536. SMALL CRAFT ADVISORY FROM 10 AM TO 6 PM EDT TUESDAY FOR ANZ535- 536.
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&& $$ SYNOPSIS...HTS NEAR TERM...HTS SHORT TERM...GMS LONG TERM...DFH AVIATION...GMS/HTS/DFH MARINE...GMS/HTS/DFH TIDES/COASTAL FLOODING...HTS

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