Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 241428 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1028 AM EDT WED SEP 24 2014 .SYNOPSIS... HIGH PRESSURE WILL EXIT OFF THE NEW ENGLAND COAST THIS AFTERNOON...AS LOW PRESSURE APPROACHES FROM THE ATLANTIC COAST. THIS SYSTEM WILL MOVE ALONG THE ATLANTIC COASTLINE...ACROSS THE MID-ATLANTIC REGION AND THEN OFF THE COAST INTO EARLY THURSDAY. HIGH PRESSURE IS ON TAP FOR THIS WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... AFTER ANALYSIS OF QPF FROM MODELS/RADAR TRENDS/SATL IMAGERY...WILL BE GOING WITH SREF/ECMWF SOLN FOR THIS EVENT ATTM. INVERTED RIDGE ORIGINATING FROM STRONG HIGH PRESSURE OVER NORTHERN NEW ENGLAND WILL MAKE THIS EVENT SLOW TO EVOLVE THIS AFTERNOON. THE RIDGE WILL BREAK DOWN MID-TO-LATE AFTERNOON OVER THE DC METRO AREA...WHICH WILL ENABLE PCPN INITIATION. LOOKING FOR ONLY LIGHT RAIN THROUGH 00Z WITH AROUND 0.1" OF RAIN BY 00Z IN DC METRO...AND ABOUT 0.25" RAIN IN S MD/TIDAL POTOMAC REGION. OVER BALT METRO AND NORTHERN MD...RIDGE WILL NOT BREAK DOWN TILL EARLY EVENING...SO BALT WILL LIKELY STAY DRY THROUGH EARLY EVENING. AFTER 00Z...H85 THETA-E RIDGE AND ASSOCIATED H85 CONVERGENCE/LLVL MOISTURE ADVECTION AND LLVL JET OFF THE ATLANTIC WILL BRING AN 8 TO 12 HOUR PERIOD OF MODERATE RAIN ALONG AND EAST OF I-95...WITH LESSER AMOUNTS TO THE BLUE RIDGE. RAIN WILL BE HEAVY AT TIMES ALONG AND E OF I-95...WHICH WILL LEAD TO PONDING OF WATER TONIGHT AND SMALL FEEDER STREAMS TO APPROACH BANKFUL. WILL BE CONSIDERING OVER THE NEXT HOUR OR TWO EXTENDING THE FLOOD WATCH IN TIME THROUGH MID MORNING THURSDAY AS CUT H5 LOW WILL BE SLOW TO LEAVE REGION THURSDAY MORNING AND PCPN WILL LINGER THROUGH MID DAY. NO CHANGES IN AREAL EXTENT OF WATCH ANTICIPATED ATTM. && .SHORT TERM /THURSDAY/... AS THE LOW BEGINS TO DRIFT BACK OFF THE DELMARVA COAST INTO THU...WINDS WILL DROP OFF WHILE TURNING NELY. THIS WILL BEGIN TO DISSIPATE THE LEFTOVER PRECIP - THOUGH THE DENSE LOW CLOUDS WILL STICK AROUND FOR MUCH OF THE DAY. HIGH PRESSURE WILL PROVIDE GOOD SUBSIDENCE IN THE WESTERN HALF OF THE REGION. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... UPPER TROUGH/LOW PRESSURE WILL GRADUALLY PULL AWAY FROM THE MIDDLE ATLANTIC REGION THURSDAY NIGHT AND THE FIRST PART OF FRIDAY. STEADY RAIN IS EXPECTED TO END BY THURSDAY NIGHT BUT A FEW LINGERING SHOWERS COULD STILL HOLD ON FROM THE BALTIMORE METRO AREA AND POINTS NORTH INTO EARLY FRIDAY. IF THE SYSTEM SLOWS DOWN OR UPPER ENERGY HANGS BACK LONGER FUTURE SHIFTS MAY NEED TO EXTEND POPS FURTHER OUT IN TIME. HIGH PRESSURE WILL BUILD INTO THE MIDDLE ATLANTIC REGION LATER FRIDAY AND REMAIN IN PLACE THROUGHOUT THE UPCOMING WEEKEND. TEMPERATURES ARE EXPECTED TO MODERATE BACK INTO THE MIDDLE TO UPPER 70S WITH LOWS GENERALLY RUNNING IN THE 40S WEST TO 50S TO NEAR 60 EAST. THE NEXT TROUGH OF LOW PRESSURE COULD APPROACH THE MIDDLE ATLANTIC LATE MONDAY OR TUESDAY OF NEXT WEEK BRINGING INCREASING CLOUDS AND A CHANCE FOR SHOWERS. && .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/... VFR CONDS EARLY THIS MRNG AND INTO THE AFTN HRS. LOWER CIGS AND SHOWERS WILL ARRIVE LATE THIS EVE ACROSS MUCH OF THE AREA. SUB VFR CIGS AND RESTRICTED VSBYS IN LIGHT RAIN/SHOWERS WILL LINGER INTO THURSDAY NIGHT. CONDITIONS ARE EXPECTED TO IMPROVE BY FRIDAY AND VFR CONDITIONS ARE EXPECTED SATURDAY THROUGH MONDAY. THE NEXT LOW PRESSURE SYSTEM COULD BRING A CHANCE FOR SHOWERS AND LOWERED CIGS BY LATE MONDAY INTO TUESDAY OF NEXT WEEK. && .MARINE... WINDS HAVE ALREADY BEEN GUSTY OVER THE SRN MD BAY...SO A SCA IS IN EFFECT FOR THESE AREAS THRU MID-MRNG. WINDS WILL INCREASE OVER THE REMAINDER OF THE AREA WATERS LATER THIS AFTN...AS LOW PRESSURE APPROACHES FROM THE SOUTH. SCA BEGINS 10 AM WEDNESDAY FOR ALL THE WATERS AND CONTINUES INTO THE OVERNIGHT HRS WHILE THE LOW IS APPROACHING AND PASSING BY JUST TO THE SE OF THE BAY. PERIODS OF RAIN LATE THIS AFTN/EVE. SCA CONDITIONS WILL GRADUALLY DIMINISH THURSDAY NIGHT. HIGH PRESSURE WILL BUILD OVER THE WATERS LATER FRIDAY AND CONTINUE INTO MONDAY OF NEXT WEEK. DURING THIS TIME...WINDS ARE EXPECTED TO REMAIN BELOW SCA LEVELS. && .HYDROLOGY... EURO/NAM NEAR-TERM GUIDANCE CONTINUE TO SHOW THE ERN...AND PARTICULARLY THE EXTREME NERN SECTIONS OF THE AREA UNDER THE BEST COMBINATION OF THE MOISTURE...LIFT AND SHEAR FOR PERSISTENT MODERATE TO HEAVY RAIN. MOISTURE-RICH AIR WILL BE LOCALIZED TO THE AXIS OF HIGHEST LIFT ALONG/NEAR THE COASTLINE. NAM 250MB WINDS SHOW A NORTH/SOUTH UPPER JET DIRECTLY OVER THE ERN HALF OF THE CWA FOR GOOD UPPER DIVERGENCE. MORE IMPRESSIVE IS THE EXPECTED LOW LEVEL JET MAX W/ A DUE ELY ONSHORE FLOW OVERNIGHT THAT CREATES A THIN BUT PRONOUNCED AXIS. A SOLID 1-2 INCHES POSSIBLE ALONG THE WRN SHORE COUNTIES OF THE BAY - STORM-TOTAL - INTO EARLY THU...LOCALLY HIGHER. THESE AMOUNTS WILL TAPER OFF TO THE WEST...ALSO W/ LOCALLY HIGHER AMOUNTS EXPECTED. && .TIDES/COASTAL FLOODING... CURRENT WATER LEVELS ARE RIGHT AT OR JUST BELOW NORMAL...BUT ARE THERE BECAUSE THEY HAVE BEEN RISING FROM OVER A HALF-FOOT BELOW NORMAL OVER A DAY AGO. A SLOW/STEADY INCREASE WILL CONTINUE THRU THE DAY TODAY...THOUGH MINOR FLOODING NOT ANTICIPATED FOR UPCOMING H.T. CYCLE. WINDS WILL INCREASE LATER THIS AFTN/EVE AHEAD OF A STRENGTHENING LOW PRES SYSTEM TO OUR SOUTH. STEADY 15-25KT WINDS WILL THEN QUICKLY INCREASE WATER LEVELS ALONG THE MD CHES BAY WRN SHORE LOCALES. THE POTENTIAL FOR MINOR CF WILL INCREASE SHARPLY WHERE THE ELY WINDS BANK UP STRONGEST/LONGEST LATE TONIGHT. AS THE LOW DRIFTS NE OF THE AREA ON THU...THE WIND FIELD WILL TURN MORE NLY AND ALLOW WATER TO PUSH BACK DOWN THE BAY AND DECREASE FLOODING POTENTIAL OVER THE COURSE OF THE DAY. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...FLOOD WATCH FROM 6 PM EDT THIS EVENING THROUGH LATE TONIGHT FOR DCZ001. MD...FLOOD WATCH FROM 6 PM EDT THIS EVENING THROUGH LATE TONIGHT FOR MDZ006-007-009>011-013-014. VA...FLOOD WATCH FROM 6 PM EDT THIS EVENING THROUGH LATE TONIGHT FOR VAZ053-054. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT THURSDAY FOR ANZ533>537- 541>543. SMALL CRAFT ADVISORY UNTIL 2 PM EDT THURSDAY FOR ANZ530>532- 538>540. && $$ SYNOPSIS...GMS NEAR TERM...LEE SHORT TERM...GMS LONG TERM...KRW AVIATION...GMS/KRW MARINE...GMS/KRW HYDROLOGY...GMS/KRW TIDES/COASTAL FLOODING...GMS/KRW

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