Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 240859 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 359 AM EST SAT JAN 24 2015 .SYNOPSIS...
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LOW PRESSURE NEAR NORFOLK WILL TRACK OFF THE DELMARVA COAST THIS MORNING...REACHING THE GULF OF MAINE TONIGHT. THE NEXT LOW PRESSURE SYSTEM WILL CROSS THE AREA FROM THE WEST SUNDAY NIGHT THROUGH MONDAY. HIGH PRESSURE IS THEN EXPECTED THROUGH THE MIDWEEK.
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&& .NEAR TERM /TODAY/...
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00Z IAD SNDG COULD BEST BE DESCRIBED AS "UNIQUE" FOR THE FACT THAT BOTH THE TEMP/DWPT LN WERE EXACTLY ON FRZG FM 928 TO 777 MB. THIS IS A PRIMARY REASON WHY P-TYPES HV BEEN SUCH A MIX. E OF THE MTNS IT IS DIFFICULT TO GET MUCH ACCUMULATING SN W/ THIS SNDG TEMP PROFILE LK THIS. ALSO INTERESTING IS HOW MOST OF THE OVRNGT OBS HV TEMPS BTWN 31-34 DEG. HARD TO GET MUCH ICE ACCUM W/ THOSE TEMPS. E OF THE MTNS HV BEEN TWEAKING FCSTD SN TOTALS DOWN ALL NGT. THX TO MULTIPLE COUNTY 911 CNTRS FOR TAKING OBS FOR US. XCTPN IS FAR WRN ALLEGANY CNTY WHERE REPORT OF 4-5" IN FROSTBURG WAS RCVD. RGNL COMP RDR SHOWS THE HEAVIER PCPN/BRIGHT BANDING HAS MOVED INTO NJ. SNSH WL BE LKLY AS SLTLY COLDER AIR MOVES INTO THE AREA...BUT OBS SHOW THAT THE AIR TO THE W IS PRETTY MUCH THE SAME TEMP AS MID ATLC IS PRESENTLY SEEING. NAM MID ATLC X-SXN SHOWS AN AREA OF UVV AT 18Z WHICH COULD LEAD TO SNSH DVLPMNT...BUT ADTNL TOTALS WOULD LKLY BE UNDER 1". THIS AFTN DOWNSLOPING NWLY FLOW AFTER THE UPR TROUGH PASSES WITH GUSTS 20 TO 25 MPH AND MOST PLACES GETTING SUNSHINE BEFORE SUNSET.
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&& .SHORT TERM /TONIGHT/...
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SFC LOW PUSHES OFF TO THE NORTHEAST AND THE MAIN FORCING WITH THE UPPER LVL SHORTWAVE SHIFTS EAST. WILL MAINTAIN UPSLOPE SNOW SHOWERS OVER THE ALLEGHENY FRONT REGION WITH A WNW FLOW ON THE BACKSIDE OF THE LOW. THE SHOWERS ARE EXPECTED TO TAPER OFF AS THE WINDS BACK TO THE SW NEAR DAYBREAK SUN MORNING...BUT THE LACK OF PCPN WILL BE SHORT LIVED AS AN ALBERTA CLIPPER QUICKLY APPROACHES THE REGION. TEMPS SAT NIGHT NEAR NORMAL...WITH EVERYWHERE IN THE UPPER 20S TO RIGHT AROUND 30.
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&& .LONG TERM /SUNDAY THROUGH FRIDAY/...
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INCREASED POPS AND MODIFIED FORECAST SNOWFALL AMTNS FOR LATE SUN INTO MON. THE BULK OF THE ACTIVITY STILL EXPECTED DURING THE OVERNIGHT HRS INTO THE EARLY MRNG HRS/FIRST HALF OF MON. HOWEVER...THIS LOOKS TO BE A TRANSITIONAL SYSTEM LIKE THE FEATURE FROM A FEW DAYS AGO - ONLY MORE INTENSE FROM START TO FINISH. MOST CLIPPER SYSTEMS MOVE QUICKLY AND THIS WILL BE NO EXCEPTION...BUT INSTEAD OF A DIRECT PATH TO THE MID-ATLC - THE UPPER FEATURE WILL BE FORCED SWD FOR A BRIEF DECELERATION PERIOD OVER THE UPPER MIDWEST. WHILE SPREADING SNOW SHOWERS ACROSS THE OHIO VLY AND WAITING FOR THE OTHER POTENT NRN ATLC SYSTEM TO MOVE FURTHER OFF THE COAST...THE FEATURE WILL MAKE A DIVE TOWARD THE SRN APLCNS. ALL GUIDANCE IS IN GOOD AGREEMENT ON THIS...W/ ONLY SLIGHTLY VARYING DIFFERENCES IN THE OVERALL INTENSITY AND EXACT TRACK. THE EURO HOWEVER MAKING A BIGGER EFFORT FOR THE TRANSITIONAL PHASE DIRECTLY OVER OUR AREA LATE SUN INTO EARLY MON. THE LATEST RUN AND EVEN MORE RECENT ONES HAVE EFFECTIVELY DISSIPATED THE WRN PRECIP TO RECONVENE IT OVER THE ERN HALF OF THE AREA/CHESPKE BAY. THE GFS ON THE OTHER HAND WRINGS OUT MOST OF IT`S PRECIP - IN THIS CASE SNOW - OVER THE WRN HALF OF THE AREA THEN DISPLACES THE FORCING OFF THE COAST W/ ONLY LIGHT/INTERMITTENT SNOWS OVER THE ERN HALF OF THE AREA DURING THE DAY ON MON. MAY NEED TO CONSIDER WINTER STORM WATCHES FOR PORTIONS OF THE AREA...ESPEC THE WRN SECTIONS OF THE CWA - CERTAINLY THE APLCNS AND POSSIBLY INTO THE SHEN VLY/BLUE RIDGE IF GUIDANCE COMES IN BETTER AGREEMENT W/ QPF/TIMING/PLACEMENTS. DIRECTLY BEHIND THE EXITING AND STRENGTHENING COASTAL SYSTEM WILL BE A SECONDARY UPPER WAVE THAT GETS PULLED DOWN ACROSS THE GREAT LAKES TOWARD THE MID-ATLC ON TUE. THE FEATURE ITSELF WILL BE DISSIPATING LATE MON NIGHT UPON APPROACH TO THE UPPER MIDWEST...CARRYING A GOOD SHOT OF COLD AIR AND ENOUGH LOW LEVEL MOISTURE TO CREATE SCATTERED SNOW SHOWERS. AS THE WAVE PULLS AROUND THE BASE OF THE UPPER TROUGH...THE SNOW SHOWERS WILL SWING ACROSS THE MID-ATLC DURING THE DAYTIME HRS TUE BUT LIKELY DISSIPATING TOWARD THE LATTER HALF OF THE DAY. AS THIS UPPER WAVE TRANSITIONS OFF THE COAST...THE MOISTURE WILL BE CUT OFF QUICKLY AND PRECIP WILL END - UNTIL YET ANOTHER UPPER WAVE APPROACHES FROM THE NORTH ON WED. THIS FEATURE WILL BE LESS LIKELY TO AFFECT THE AREA OUTSIDE OF SOME UPSLOPE MTNS SNOWS BUT WILL REINFORCE THE COLDER AIRMASS DURING THE MIDDLE OF THE WEEK. THE NEXT WX CONCERN FOR THE EXTENDED IS THE COLD. THE TWO EXTRA WAVES OF REINFORCING COLD AIR FROM THE NORTH TUE AND AGAIN ON WED WILL NOT ONLY KEEP OUR DAILY HIGHS MAXED-OUT NEAR THE FREEZING MARK BUT ALLOW OVERNIGHT LOWS TO DROP WELL INTO THE TEENS AND 20S ACROSS THE REGION...SOME SINGLE DIGITS OVER THE APLCNS. HIGH PRES BRIEFLY BUILDS IN FROM LATE WED INTO THU AND A RELATIVE WARM-UP BUT ONLY INTO THE U30S ON THU AFTN. ANOTHER CLIPPER WILL BE WELL ON ITS WAY TOWARD THE AREA DURING LATTER HALF OF THE WEEK...MOVING ACROSS THE REGION LIKELY LATE THU INTO FRI ACCORDING TO THE RECENT GFS AND EURO RUNS. NOT A COMPLETELY SIMILAR SOLN BETWEEN THEM BUT ELEMENTS OF THE SAME LOOK...EXCEPT THE GFS HOLDS A MORE COMPACT UPPER WAVE THAT SLIDES OVER THE AREA AND BRINGS MORE PRECIP TO OUR REGION.
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&& .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/...
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IFR CONDS THIS MRNG. THE BULK OF THE PRECIPITATION MOVES OUT BY NOON. CIGS WILL IMPROVE THIS AFTN WITH NWLY FLOW GUSTING 20 TO 25 KT. VFR CONDITIONS TNGT. A CLIPPER SYSTEM WILL QUICKLY ARRIVE DURING THE DAYTIME HRS ON SUN...MAINLY THE LATTER HALF W/ MAINLY SNOW UPON ARRIVAL. PERIODS OF SNOW FOR THE REGION LATE SUN INTO MON. IFR CONDS OR LOWER W/ THE HEAVIEST ACTIVITY...THEN GUSTY NLY WINDS EARLY MON AS A LOW DEVELOPS AND STRENGTHENS OFF THE COAST. LINGERING SNOW SHOWERS ON TUE AND SOME SUB-VFR CONDS FOR THE FIRST HALF OF THE DAY. ACTIVITY MOVING OFF THE COAST BY MID-WEEK. ANOTHER COLD/POTENTIALLY SNOWY CLIPPER SYSTEM ON FRI.
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&& .MARINE...
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SCA IN EFFECT FOR SRN PORTIONS OF THE WATERS...AND THEN ALL WATERS TODAY WITH 20 TO 25 KT GUSTS EXPECTED. LINGERING SCA GUSTS UP TO 20 KT THIS EVENING...THEN DECREASING OVERNIGHT.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...WINTER STORM WARNING UNTIL NOON EST TODAY FOR MDZ501. WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR MDZ003>006- 011-502>508. VA...WINTER STORM WARNING UNTIL NOON EST TODAY FOR VAZ503-504. WINTER WEATHER ADVISORY UNTIL 10 AM EST THIS MORNING FOR VAZ025-026-036-037-508. WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR VAZ027>031- 038>040-050>053-501-502-505>507. WV...WINTER STORM WARNING UNTIL NOON EST TODAY FOR WVZ501>506. WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR WVZ050>053- 055. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS EVENING FOR ANZ532>534-537-540>543. SMALL CRAFT ADVISORY FROM NOON TODAY TO 6 PM EST THIS EVENING FOR ANZ530-531-535-536-538-539.
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&& $$ PRODUCTS...WOODY!/GMS

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