Area Forecast Discussion
Issued by NWS Sterling, VA

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
972 FXUS61 KLWX 040207 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 907 PM EST WED FEB 3 2016 .SYNOPSIS...
-- Changed Discussion --
A COLD FRONT SLOWLY MOVES THROUGH THE REGION TONIGHT BEFORE STALLING JUST OFFSHORE THROUGH FRIDAY. MULTIPLE LOW PRESSURES WILL RIDE THIS FRONT WITH HIGH PRESSURE BUILDING IN FOR THE WEEKEND. LOW PRESSURE IMPACTS THE REGION THE FIRST HALF OF NEXT WEEK.
-- End Changed Discussion --
&& .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
-- Changed Discussion --
AT 8 PM...COLD FRONT WAS NEARING THE WESTERN SLOPES OF THE APPALACHIANS. HEAVIEST RAIN HAS NOW PUSHED TO THE EAST OF THE CWA EXCEPT THE LOWER SOUTHERN MD WATERS. INTERESTING PRESSURE-RISE FEATURE IMMEDIATELY BEHIND THE SHOWERS RESULTED IN BRIEF WIND GUSTS AND SCOURING OUT OF THE FOG. HOWEVER...NOW THAT WINDS HAVE SUBSIDED...FOG HAS REFORMED...ESPECIALLY NORTHERN AREAS. ISSUED A DENSE FOG ADVISORY AS THIS AREA ALIGNS WITH NARRE GUIDANCE FOR LOW VSBY. WILL MONITOR FOR EXPANSION...AS LLVLS REMAIN SATURATED AHEAD OF THE FRONT. ADVISORY IN EFFECT THROUGH 7 AM...ALTHOUGH MAY START TO SEE IMPROVEMENT AS EARLY AS 1 AM IN THE WEST AS WINDS SHIFT TO THE WEST. EDGE OF RAIN WILL REMAIN JUST SE THROUGH THE NIGHT...WITH RIPPLES OF SHORTWAVE ENERGY POSSIBLE BRINGING SOME SHOWERS BACK TO THE NW. THINK MOST ACTIVITY WILL STAY SE OF DC. THEREFORE WE/RE NOT EXPECTING ANY MORE RAIN INTO THE STREAMS. WILL MONITOR LEVELS OVER THE NEXT FEW HOURS AND MAY BE ABLE TO PEAL BACK SOME OF THE WATCH. OF COURSE THE LARGER RIVERS WILL REMAIN A CONCERN THROUGH THE NEXT COUPLE OF DAYS. HYDRO SECTION BELOW. TEMPERATURES NEARLY STEADY UNTIL FROPA. SLIGHT CHANCE OF UPSLOPE SNOW SHOWER LATE.
-- End Changed Discussion --
&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/... 12Z MODEL GUIDANCE HAS THE COLD FRONT JUST SOUTH OF THE AREA BY 12Z THURS. HOWEVER...WITH THE UPPER LVL TROUGH STILL WELL OFF TO THE WEST...THE LACK OF FORCING WILL NEARLY STALL THE BOUNDARY JUST OFFSHORE THURS INTO FRI. MEANWHILE...MULTIPLE SHORTWAVES RIDING THE FLOW WILL RESULT IN MULTIPLE LOWS RIDING THE STALLED FRONT...CONTINUING THE PCPN THREAT...ESP SOUTH AND EAST OF DC METRO DURING THIS TIME PERIOD. THE LATEST MODEL SUITE DOES DIVERGE ON THE SOLUTIONS ON THE NORTHERN EXTENT OF THE PCPN AND AS SUCH...WILL MAINTAIN LOWER POPS UNTIL CONFIDENCE OF COVERAGE FOR LATER THURS AND THURS NIGHT. NW WINDS COULD ALSO PRODUCE ISO-SCT UPSLOPE SNOW SHOWERS...BUT WITH LACK OF MOISTURE IN SNOW GROWTH ZONE...NOT ANTICIPATING MORE THAN A COUPLE TENTHS OF AN INCH FOR PORTIONS OF THE POTOMAC HIGHLAND FROM THURS MORNING THRU THURS NIGHT. LOSS OF MOISTURE OF DRIER AIR FINALLY MOVES IN SHOULD CUT OFF ANY SNOW SHOWERS BY FRI MORNING. THE UPPER LVL TROUGH FINALLY SWINGS THRU THURS NIGHT...WITH TEMPS RETURNING BACK TO NEAR NORMAL BY FRI. BEHIND THE TROUGH...RIDGING AND SFC HIGH PRESSURE BUILDING IN FROM THE WEST WILL PUSH THE LOW PRESSURE SYSTEM OUT OF THE AREA AND BRING IN A PERIOD OF DRY WX. THE RIDGE AXIS TRAVERSES THE REGION QUICKLY AND BY THE COMING WEEKEND WILL SEE RETURN FLOW SETTING UP. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... HIGH PRESSURE OVER THE MID ATLANTIC WILL BECOME ELONGATED FROM THE TENNESSEE VALLEY TO THE OPEN WESTERN ATLANTIC OCEAN SATURDAY NIGHT. A COLD FRONT WILL SAG ACROSS THE EASTERN GREAT LAKES SATURDAY NIGHT BEFORE PUSHING TO THE EAST COAST. AT THE TAILEND OF THIS FRONT...THERE IS THE POTENTIAL FOR AN AREA OF LOW PRESSURE TO DEVELOP AND INTENSIFY NEAR THE CAROLINAS. THERE IS LOW CERTAINTY AS TO WHERE AND WHEN THIS LOW COULD DEVELOP. IT DOES APPEAR THAT THE LOW WILL DEVELOP TOO LATE TO HAVE A SIGNIFICANT IMPACT ON OUR WEATHER. ADDITIONAL SHORTWAVE ENERGY WILL BE DIVING INTO THE CENTRAL U.S. AND WESTERN GREAT LAKES...ALLOWING THIS SYSTEM TO PUSH FARTHER EAST THAN NORTH. THIS WOULD KEEP THE LOW TOO FAR TO OUR SOUTH BUT THIS WILL HAVE TO BE MONITORED SINCE IT IS STILL SEVERAL DAYS OUT. THE SYSTEM DIVING INTO THE CENTRAL U.S. SUNDAY MAY DEVELOP INTO A COASTAL LOW DURING THE EARLY PORTION OF NEXT WEEK. LATEST DETERMINISTIC GFS AND ECMWF SHOW THIS HAVING A BETTER CHANCE OF IMPACTING OUR AREA. THE GEFS MEAN SHOWS A STRONG UPPER-LEVEL TROUGH OVERHEAD WHICH WOULD ALSO SUPPORT THE POSSIBILITY OF A COASTAL LOW. CONFIDENCE IS HIGH FOR A HIGH AMPLITUDE PATTERN WITH A POTENT UPPER- LEVEL TROUGH OVERHEAD SATURDAY THROUGH TUESDAY...BUT THE DETAILS AND TIMING OF THE SHORTWAVE ENERGY ARE HIGHLY UNCERTAIN WHICH LEADS TO A LOW CONFIDENCE FORECAST. HOWEVER...AS OF NOW IT APPEARS THAT SATURDAY AND SUNDAY WILL TURN OUT DRY AND SEASONABLY CHILLY. A COASTAL STORM MAY BRING THE CHANCE FOR WINTRY PRECIPITATION TO THE AREA EARLY NEXT WEEK. && .AVIATION /02Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --
LOW CONFIDENCE FORECAST THROUGH THE LATE EVENING HOURS IN A WAIT- AND-SEE MODE TO DEVELOPING CONDITIONS. WIND SURGE BEHIND RAIN SHIELD BRIEFLY BROUGHT IMPROVEMENT. HOWEVER FRONT IS STILL TO WEST AND ABUNDANT LLVL MOISTURE LEADING TO REDEVELOPMENT OF FOG AND STRATUS. GUIDANCE HAS METRO AREA RIDING THE LINE OF LOWEST CONDITIONS. HAVE AT LEAST A PERIOD OF IFR AT ALL TERMINALS. COLD FRONT MOVES THROUGH BETWEEN 06-09Z TONIGHT...BRINGING A SHIFT IN THE WINDS TO THE NW AND GRADUALLY IMPROVING CONDITIONS. GUSTS 20-25 KTS WILL BE PSBL WITH THE WIND SHIFT AS WELL. NW FLOW AND VFR CONDITIONS LAST THRU FRI. VFR CONDITIONS SATURDAY NIGHT AND SUNDAY. WINDS SOUTHWEST WINDS AROUND 10 KNOTS. WINDS BECOMING NORTHWEST 10 TO 15 KNOTS GUSTS TO 20 KNOTS.
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
VARIBALE WIND CONDITIONS ON THE WATERS LATE THIS EVENING...AND EXPECT THIS TO CONTINUE UNTIL A COLD FRONT PUSHES THROUGH LATE TONIGHT. EXPECT A SURGE OF WINDS BEHIND THIS...POTENTIALLY REACHING SCA LEVELS. LOW CONFIDENCE ON TIMING OF CURRENT HEADLINES AND THESE MAY NEED SOME ADJUSTMENT. SCA CONDITIONS WILL CONTINUE ON ALL WATERS THURSDAY MORNING... THROUGH THE SECOND HALF OF THE DAY. WINDS WILL INCREASE THURS NIGHT WITH THE CAA PRESSURE SURGE...SO ANOTHER SCA MAY BE NEEDED THURS NIGHT AND INTO FRIDAY AS HIGH PRESSURE BUILDS IN. NO MARINE HAZARDS SATURDAY NIGHT. SMALL CRAFT ADVISORIES POSSIBLE SUNDAY.
-- End Changed Discussion --
&& .HYDROLOGY...
-- Changed Discussion --
RAIN HAS ENDED ACROSS THE MOST VULNERABLE BASINS. RAINFALL AMOUNTS RANGE FROM A HALF INCH TO INCH ACROSS THE POTOMAC...SHENANDOAH AND RAPPAHANNOCK BASINS WITH ISOLATED AMOUNTS UP TO AN INCH AND A QUARTER. THIS COUPLED WITH TEMPERATURES AND DEWPOINTS IN THE 40S/50S ALLOWED MUCH OF THE REMAINING SNOW TO MELT AND FURTHER SATURATE THE SOIL. SMALL AND LARGE STREAMS ARE STILL ON THE RISE THIS EVENING DUE TO THE COMBINATION OF RAIN AND SNOWMELT. PARTIAL ICE BLOCKAGES MAY STILL BE A FACTOR...ESPECIALLY IN THE EASTERN WV PANHANDLE AND NORTHERN MARYLAND. ICE WAS ALSO REPORTED MOVING DOWN THE MIDDLE POTOMAC YESTERDAY BUT IT DOES NOT APPEAR IT IS CAUSING A SUBSTANTIAL BLOCKAGE AT THIS TIME. WE HAVE SEEN RISES ON THE LARGER RIVERS AS WELL AS FLOODING ON SOME SMALL STREAMS IN NORTHERN VA...EASTERN WV...AND NORTHERN MD. THE THREAT OF URBAN FLOODING/PONDING SHOULD NO LONGER BE AN ISSUE OTHER THAN RESIDUAL STANDING WATER. RIVER FLOOD WARNINGS ARE CURRENTLY IN EFFECT FOR CACAPON...OPEQUON...MONACACY...POTOMAC FROM POINT OF ROCKS TO EDWARDS FERRY...SENECA CREEK AND SHENANDOAH AT MILLVILLE FOR FLOODING TONIGHT AND TOMORROW. A RIVER FLOOD WATCH CONTINUES FOR POTOMAC RIVER INCLUDING HARPERS FERRY AND LITTLE FALLS. PLEASE SEE FLOOD WATCH AND FLOOD WARNING PRODUCTS FOR MORE INFORMATION.
-- End Changed Discussion --
&& .TIDES/COASTAL FLOODING...
-- Changed Discussion --
ANOMALIES ARE STILL 1-1.5 FT ABOVE NORMAL. WHILE IT DOES NOT APPEAR THIS WILL CAUSE ANY FLOODING ISSUES...WILL HAVE TO WATCH ONE MORE HIGH TIDE CYCLE BEFORE NW WINDS CAUSE DECREASING WATER LEVELS THURSDAY.
-- End Changed Discussion --
&& .LWX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
DC...FLOOD WATCH UNTIL 6 AM EST THURSDAY FOR DCZ001. MD...FLOOD WATCH UNTIL 6 AM EST THURSDAY FOR MDZ013-014-503>506. DENSE FOG ADVISORY UNTIL 7 AM EST THURSDAY FOR MDZ003>006-011- 502>508. FLOOD WATCH THROUGH THURSDAY AFTERNOON FOR MDZ003>006-011-507- 508. VA...FLOOD WATCH UNTIL 6 AM EST THURSDAY FOR VAZ052>056-505-506. DENSE FOG ADVISORY UNTIL 7 AM EST THURSDAY FOR VAZ505-506. WV...DENSE FOG ADVISORY UNTIL 7 AM EST THURSDAY FOR WVZ050>053-504. FLOOD WATCH THROUGH THURSDAY AFTERNOON FOR WVZ051>053. MARINE...SMALL CRAFT ADVISORY UNTIL 1 AM EST THURSDAY FOR ANZ532>534- 537-543. SMALL CRAFT ADVISORY FROM 6 AM TO 1 PM EST THURSDAY FOR ANZ532- 533-536-538>542. SMALL CRAFT ADVISORY FROM 6 AM TO 6 PM EST THURSDAY FOR ANZ534- 537-543. SMALL CRAFT ADVISORY FROM 4 AM TO 1 PM EST THURSDAY FOR ANZ530- 531.
-- End Changed Discussion --
&& $$ SYNOPSIS...SEARS NEAR TERM...ADS SHORT TERM...SEARS LONG TERM...KLW AVIATION...SEARS/ADS/KLW MARINE...SEARS/ADS/KLW HYDROLOGY...ADS/HAS/JE TIDES/COASTAL FLOODING...ADS

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.