Area Forecast Discussion
Issued by NWS Sterling, VA

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195 FXUS61 KLWX 060120 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 920 PM EDT THU MAY 5 2016 .SYNOPSIS... LOW PRESSURE IMPACTS THE REGION TO END THE WEEK WITH A COLD FRONT SWINGING THROUGH SUNDAY. HIGH PRESSURE BRIEFLY BUILDS IN...WITH A WARM FRONT LIFTING NORTH FIRST HALF OF NEXT WEEK. && .NEAR TERM /THROUGH FRIDAY/... HAD A DRY LT AFTN/ELY EVNG...BUT RADAR ACTIVITY BGNG TO RESUME AS MID LVL MSTR/ENERGY STREAMS NWD WHILE SFC FLOW REMAINS NELY. IS A GOOD OVERRUNNING SETUP...AND SEE ITS RESULTS FILLING IN W OF I-95. THUS FAR ANY PCPN HAS BEEN LGT. RAP/HRRR BOTH SUGGEST THAT SOME OF THE STEADIER RAFL ACRS SERN VA WL APPROACH CWFA OVNGT. CUT BACK POPS SUBSTANTIALLY ERLR THIS EVENING...BUT TRENDED THOSE REDUCED POPS BACK TO LKLY BY MIDNGT...W/ LKLY/CAT POPS OVNGT. HEADING INTO FRIDAY...UPPER LVL LOW PIVOTS TO THE SOUTH AND THEN EAST...BCMG NEARLY STATIONARY OVER THE DELMARVA REGION FOR MOST OF FRI INTO SATURDAY. A SHORTWAVE CURRENTLY OVER WESTERN CANADA WILL BE NEEDED TO EVENTUALLY PUSH THIS NEARLY STALLED CLOSED LOW OUT LATER THIS WEEKEND. BEFOREHAND HOWEVER...EXPECTING AN INCREASE IN COVERAGE AND INTENSITY OF RAIN SHOWERS TONIGHT ACROSS THE ENTIRE CWA...LASTING THRU A GOOD PORTION OF FRIDAY AS THE MAIN FORCING WITH THE UPPER LVL LOW SWINGS AROUND THE EASTERN PERIPHERY RIGHT THRU THE MID- ATLANTIC. MEANWHILE AT THE SFC...SFC LOW PUSHING OFF THE CAROLINA COAST WILL MOVE TO THE NORTHEAST...WITH A SECONDARY LOW FORMING JUST OFF THE SE VA COAST. CLOUDS AND NLY FLOW WILL KEEP TEMPS ON THE COOLER SIDE WITH TEMPS BELOW NORMAL. && .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/... THE UPPER LVL LOW REMAINS POSITIONED OVER THE REGION FOR THE TIME PERIOD...WITH THE SFC LOW HAVING BACKED OVER THE DELMARVA REGION...AND REMAINING NEARLY STATIONARY AS WELL. THIS WILL KEEP THE CHC FOR PCPN IN THE FORECAST THRU SATURDAY...THOUGH WITH THE BETTER FORCING WITH THE UPPER LVL LOW TO THE NE OF THE CWA...HEAVIER RAIN THREAT WILL BE ON THE LOWER END. SHORTWAVE DIGGING SOUTH OVER THE GREAT LAKES REGION SAT NIGHT WILL BRING AN ASSOCIATED SFC COLD FRONT THRU THE REGION...WHICH WILL CONTINUE TO BRING THE CHC OF RAIN SHOWERS TO THE AREA AS WELL AS FINALLY BEING ABLE TO NUDGE THE CLOSED LOW AND SFC LOW OUT OF THE MID-ATLANTIC. && .LONG TERM /SUNDAY THROUGH THURSDAY/... COLD FRONT WILL MOVE ACROSS THE REGION SUN MORNING WITH A CHANCE OF RAIN SHOWERS. THE FRONT WILL STALL TO OUR SOUTH OVER THE CAROLINAS AS DRY CONDITIONS BUILD OVER OUR REGION LATER ON SUN AND INTO MON. THE FRONT WILL LIFT AS A WARM FRONT MON NIGHT INTO TUE BRINGING BACK THE CHANCE OF SHOWERS. GUIDANCE DIFFERS FOR TUES AND INTO WED AS OF PRECIP AND POSITION OF A SFC LOW THAT WILL MOVE E OR NE FROM THE PLAINS. ANOTHER COLD FRONT EXPECTED ON THU. HIGH TEMPS WILL BE IN THE 70S AND LOW 80S AND LOW TEMPS INCREASING FROM THE 40S AND 50S INTO THE UPR 50S AND LOW 60S. && .AVIATION /01Z FRIDAY THROUGH TUESDAY/... CIGS MANAGED TO REACH VFR HGTS LT TAFTN...BUT THE DESCENT BACK TO MVFR HAS BEGUN AS RAIN RETURNS TO TERMINALS. ATTM ANY PCPN IS LGT...AND FLGT RESTRICTIONS SPOTTY. BELIEVE IT WILL FILL IN AND LOWER OVERNGT AS MID LVL MSTR/ENERGY COMES AT AREA FROM THE SOUTH WHILE SFC FLOW REMAINS NLY. HV DROPPED OVNGT CONDS TO IFR. HV RELATIVELY HIGH CONFIDENCE IN ITS OCCURENCE...BUT LWR CONFIDENCE AT ONSET TIMING. SUB-VFR CONDITIONS EXPECTED THRU SAT TO ACCOUNT FOR ON/OFF RAIN SHOWERS AND STRATUS. HV TAKEN PREVAILING CONDS IN TAFS ON FRI BACK TO MVFR FOR THE DAY...BUT LCL IFR STILL PSBL. CONDS SHUD DROP BACK TO IFR /OR LWR/ FRI NGT. ANTICIPATE SIMLR PTTN SAT. SUB-VFR CONDITIONS POSSIBLE EARLY ON SUN AS COLD FRONT MOVES THROUGH. VFR CONDITIONS EXPECTED LATER ON SUN AND INTO MON. SUB- VFR PSBL MON NIGHT INTO TUES AS WARM FRONT BRINGS BACK CHANCE OF SHOWERS TO THE REGION. && .MARINE... MODEL GDNC CONTS TO SUGGEST THAT OCNL GUSTS MAY JUST EXCEED SCA THRESHOLDS OVERNIGHT...SO HV CONTD SCA INTO FRI MORNING. SUB-SCA ON ALL WATERS FRI-SAT. SCA CONDITIONS EXPECTED SUN AS A RESULT OF A COLD FRONT...THEN WINDS WILL DECREASE. EXPECTING SUB-SCA CONDITIONS FOR MON AND TUE. && .TIDES/COASTAL FLOODING... WATER DEPARTURES ONLY AROUND A FOOT IN THE NORTHERN CHESAPEAKE BAY...BUT ITS UP TO 1.5 FT IN THE MID BAY. IN ADDITION...AS MID LEVEL LOW PRESSURE ROTATES JUST SOUTH OF THE MOUTH OF THE BAY...AND INITIATES A SURFACE REFLECTION...ADDITIONAL WATER SHOULD BE DRAWN INTO THE ESTUARY. AT THE VERY LEAST...THIS FEATURE WILL INHIBIT WATER ALREADY PRESENT FROM DRAINING OUT. AS A RESULT... WE/LL HAVE A SETUP FAVORABLE FOR A PROLONGED EVENT. WITH THAT IN MIND...HAVE BEEN MAKING INCREMENTAL ADJUSTMENTS TO ADVISORIES. AT ST GEORGE ISLAND...BASED ON CURRENT DEPARTURES AND A BLEND OF LATEST MODEL GUIDANCE...THE MDT CRITERIA CERTAINLY LOOKS LIKE ITS WITHIN REACH. CURRENT FORECAST HAS THE CRITERIA TOUCHED. BASED ON CONFIDENCE...THATS REASON ENOUGH TO ISSUE A WARNING FOR THE OVERNIGHT TIDE CYCLE. ELEVATED WATER WILL CONTINUE FOR A COUPLE OF CYCLES THEREAFTER. FOR NOW...ONLY INCLUDED ONE IN AN ADVISORY. THE OTHER PLACE WHERE A WARNING IS POSSIBLE OVERNIGHT/EARLY FRI AM IS AT ANNAPOLIS. HOWEVER...CONFIDENCE LVL IS LOWER. THEREFORE... HAVE AN ADVISORY IN PLACE OVERNIGHT...WITH A CREST A COUPLE OF INCHES BELOW MDT FLOOD. THE ELY MORNING TIDE IN THE BAY IS THE HIGHER OF THE TWO ASTRONOMICALLY...AND THE DIFFERENCE BETWEEN THE TWO IS A HALF- FOOT. THAT IS RESULTING IN STAGGERED ADVISORIES...WITH THE AM CYCLE THE ONE THAT LKLY WILL TRIGGER FLOODING. THIS IS THE CASE FOR CALVERT...AND HAVE ADDED BALTIMORE CO/CITY TO THE LIST OF ADVYS ON FRI MORNING. HOWEVER...THE ADDED WATER LVL DEPARTURE NEAR SOLOMONS SUPPORTS A PROLONGED MULTI-CYCLE ADVY FOR CALVERT CO...THRU FRI PM. THERE IS MUCH LESS DIFF IN WATER LEVEL BETWEEN TIDE CYCLES IN THE UPPER TIDAL POTOMAC. GUIDANCE SUGGESTING A PROLONGED MINOR EVENT...AND HAVE ISSUED ONE ADVY FOR THREE TIDE CYCLES...COVERING THRU FRI NIGHT. BASED ON MODEL GUIDANCE...EVEN THIS MAY NOT BE LONG ENOUGH. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...COASTAL FLOOD ADVISORY UNTIL MIDNIGHT EDT FRIDAY NIGHT FOR DCZ001. MD...COASTAL FLOOD ADVISORY UNTIL 6 PM EDT FRIDAY FOR MDZ018. COASTAL FLOOD ADVISORY FROM 4 AM TO 10 AM EDT FRIDAY FOR MDZ011. COASTAL FLOOD ADVISORY UNTIL 9 AM EDT FRIDAY FOR MDZ014. COASTAL FLOOD WARNING UNTIL 6 AM EDT FRIDAY FOR MDZ017. COASTAL FLOOD ADVISORY FROM 10 AM TO 6 PM EDT FRIDAY FOR MDZ017. VA...COASTAL FLOOD ADVISORY UNTIL MIDNIGHT EDT FRIDAY NIGHT FOR VAZ054. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 9 AM EDT FRIDAY FOR ANZ534-543. && $$ SYNOPSIS...SEARS/IMR NEAR TERM...HTS/SEARS SHORT TERM...SEARS LONG TERM...IMR AVIATION...HTS/SEARS/IMR MARINE...HTS/SEARS/IMR TIDES/COASTAL FLOODING...HTS

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