Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 291855 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 255 PM EDT FRI MAY 29 2015 .SYNOPSIS... HIGH PRESSURE WILL REMAIN OFFSHORE TODAY. SOUTHERLY WINDS WILL CONTINUE TO BRING WARM AND HUMID CONDITIONS TO THE MID-ATLANTIC THROUGH SATURDAY. A COLD FRONT WILL ARRIVE SUNDAY AND STALL OVER THE AREA THROUGH MONDAY. HIGH PRESSURE IS EXPECTED TO SLIDE INTO THE REGION FOR THE MIDDLE PART OF NEXT WEEK. && .NEAR TERM /TONIGHT/... AS DSCD ERLR...MRNG SNDG SHOWED VERY LGT WINDS UP THRU THE ATMOSPHERIC COLUMN WHICH WOULD LEND ITSELF TO STRAIGHT UP AND DOWN CELLS WHICH WOULD HV THE PTNL TO PRODUCE HVY RA IN A SHORT TIME WHERE CELLS POPPED UP. THIS IS WHAT WE`RE SEEING ON RDR ATTM...AND XPCT THIS TO CONT TO BE THE SITUATION INTO THE EVE HRS. AFTR THAT ANOTHER WARM NGT ON TAP FOR THE AREA. IN ERLR DSCN TDA I WROTE THAT DC IS TIED FOR THE WARMEST MAY ON RECORD AND THE 2ND WARMEST FOR MIN TEMPS. LOWS TNGT GNRLY IN M60S..L70S IN THE CITIES. && .SHORT TERM /SATURDAY/... AREA RMNS IN THE SAME AIR MASS SAT - CD FNT RMNS TO OUR NW BUT IS WORKING ITS WAY IN THIS DIRECTION. BEST CHC OF TSTMS WL BE IN THE AFTN IN THE WRN PART OF THE CWA. HIGHS WL AGN BE IN THE MU80S. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... ON SATURDAY NIGHT...THE UPPER LEVEL RIDGE OFFSHORE WILL BEGIN TO BE SUPPRESSED BY A SHORTWAVE TROUGH PUSHING THROUGH CANADA. A COLD FRONT WILL BE APPROACHING FROM THE NW...EXTENDING DOWN THE ST LAWRENCE VALLEY INTO THE SOUTHER GREAT LAKES. AFTER ANY DIURNAL CONVECTION SUBSIDES...A CHANCE OF SHOWERS WILL REMAIN NEAR THE PA BORDER FOR ANY ACTIVITY THAT RACES AHEAD OF THE FRONT. OTHERWISE JUST ANOTHER MUGGY NIGHT WITH INCREASING CLOUDS AND LOWS IN THE 60S...LOWER 70S URBAN AREAS. CONFIDENCE IN THE SUNDAY TO SUNDAY NIGHT PERIOD IS NOT PARTICULARLY HIGH AS THE COLD FRONT ADVANCES INTO THE AREA. THERE IS STILL SOME MODEL SPREAD IN HOW QUICKLY THE FRONT WILL PUSH SOUTHWARD...BUT THE OVERALL TREND HAS BEEN SLOWER. THIS MAKES SENSE BECAUSE THE FRONT WILL BECOME PARALLEL TO THE UPPER FLOW AS IT PUSHES INTO THE STRONG RIDGE. A WAVE OF LOW PRESSURE WILL ALSO MOVE ALONG THE FRONT SOMETIME IN THIS TIME PERIOD. THUNDERSTORMS SEEM LIKE A GOOD BET...BUT WILL NOT BE GOING HIGHER THAN LIKELY YET DUE TO THE TIMING UNCERTAINTY. THIS ALSO MEANS HIGH TEMPS SUNDAY WILL LIKELY BE A BIT HIGHER...AND COULD ONCE AGAIN APPROACH 90 OVER THE SE CWA WHICH WILL HAVE FAIRLY LOW PRECIP CHANCES DURING MUCH OF THE DAY. IT LOOKS LIKE ANY SEVERE POTENTIAL SUNDAY WILL BE LIMITED AND TIED TO BUILDING INSTBY AS SHEAR WILL NOT BE PARTICULARLY STRONG. A BIGGER THREAT MAY BE DUE TO HEAVY RAIN AND FLOODING DUE TO THE STALLING FRONT...DEVELOPING LLJ SUNDAY NIGHT...AND FAVORABLE UPPER DIVERGENCE IN A HIGH PWAT ENVIRONMENT. HOWEVER...A LITTLE DIFFICULT TO SAY WHICH TIME PERIOD AND WHICH PART OF THE MID-ATLANTIC WOULD HAVE THE BIGGEST THREAT AT THIS TIME. A BIG SHIFT IN THE PATTERN WILL OCCUR BEHIND A COLD FRONT EARLY NEXT WEEK. AS THE FRONT DROPS SLOWLY SOUTH...RAIN CHANCES WILL SLOWLY DIMINISH MONDAY INTO TUESDAY. MEANWHILE...HIGH PRESSURE WILL BUILD OVER NEW ENGLAND SETTING UP A COOL AIR DAMMING WEDGE ACROSS THE REGION. TEMPERATURES WILL SHIFT FROM HEAT AND HUMIDITY MORE TYPICAL OF MID-JULY TO TEMPERATURES MORE TYPICAL OF MID-APRIL. AS THE HIGH GRADUALLY SHIFTS TO THE EAST AND WEAKENS...TEMPERATURES WILL GRADUALLY REBOUND TO NEAR NORMAL LEVELS BY THE END OF THE WEEK. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... ISOLD TSTMS WL BE THE MAIN CONCERN THRU ARND 02Z. IF ONE MOVES OVR A TERMINAL XPCT BRIEF VERY HVY RAFL AND DIMINISHED VSBY. FOG PSBL LATE TNGT AT CHO/IAD/MRB. THERE WL BE CHCS FOR TSTMS AGN SAT AFTN...BEST CHC AT MRB. TIMING OF COLD FRONT SUNDAY-SUNDAY NIGHT A BIT SLOWER...BUT THUNDERSTORMS WILL STILL BE LIKELY AT SOME POINT DURING THE TIME PERIOD. HEAVY RAIN POSSIBLE...SO IFR FLIGHT CONDITIONS MORE LIKELY THAN THEY HAVE BEEN WITH RECENT SCATTERED STORMS. NELY FLOW 10 KT OR SO MON-TUE. SUB-VFR PSBL IN LOW CIGS/-RA. && .MARINE... WINDS RMN BLO SCA VALUE THIS AFTN/TNGT. ISOLD TSTMS MAY IMPACT THE WATERS THRU MID EVE. THESE COULD PRODUCE VERY HVY RAFL. SRLY WINDS ARE XPCTD TO INCRS SAT AHD OF A CD FNT. AN SCA IS IN EFFECT. WINDS WILL DECREASE SOME SATURDAY NIGHT AND WILL KEEP SCA IN PLACE AS ORIGINALLY ISSUED...WHICH WILL BE IN EFFECT FOR THE MAIN CHANNEL OF THE BAY THROUGH THE NIGHT. SOUTHERLY FLOW ON SUNDAY MAY APPROACH SCA CONDITIONS BUT WILL BE MARGINAL. COLD FRONT PASSAGE APPEARS IT WILL BE A BIT SLOWER...BUT THUNDERSTORMS WILL STILL EVENTUALLY BECOME LIKELY SUNDAY AFTERNOON/NIGHT AND POSE A LOCALIZED WIND THREAT. GRADIENT WIND FIELD UNCERTAIN BY SUNDAY NIGHT AND WILL DEPEND ON FRONTAL POSITION. HIGH PRESSURE BUILDING IN BEHIND A COLD FRONT WILL LIKELY PUSH NORTHEASTERLY WINDS TO SMALL CRAFT ADVISORY LEVELS MONDAY INTO TUESDAY. && .CLIMATE... HOT TEMPERATURES WILL CONTINUE THROUGH SATURDAY...FOLLOWED BY WELL BELOW NORMAL TEMPERATURES EARLY NEXT WEEK. BELOW IS A LIST OF RECORD DAILY WARM TEMPERATURES FOR MAY 29TH AND 30TH. .......RECORD WARM TEMPERATURES FOR DCA........ DATE...RECORD HIGH...........RECORD HIGH MIN... 5/29...97 (1991/1969)........74 (1991)......... 5/30...98 (1991).............74 (1991)......... .......RECORD WARM TEMPERATURES FOR BWI........ DATE...RECORD HIGH...........RECORD HIGH MIN... 5/29...97 (1969).............71 (1908)......... 5/30...98* (2011/1991).......72 (1895)......... *ALSO HIGHEST OBSERVED MAY MONTHLY TEMPERATURE .......RECORD WARM TEMPERATURES FOR IAD........ DATE...RECORD HIGH...........RECORD HIGH MIN... 5/29...97* (1969)............69 (2012)......... 5/30...95 (2006/1991/1987)...70 (2011)......... *ALSO HIGHEST OBSERVED MAY MONTHLY TEMPERATURE BELOW IS THE LONGEST STRETCH OF CONSECUTIVE DAYS AT OR ABOVE 90 F DURING THE MONTH OF MAY. DCA...7 DAYS (05/25-05/31/1991) BWI...7 DAYS (05/25-05/31/1991) IAD...7 DAYS (05/25-05/31/1991) BWI HIT 91 DEGREES ON THURSDAY MAY 28TH. THIS WAS THEIR FIRST 90+ DEGREE DAY OF 2015 AND THE WARMEST SINCE SEPTEMBER 6TH 2014 (WHEN THEY HIT 93 DEGREES). BELOW IS A LIST OF RECORD DAILY LOW MAXIMUM TEMPERATURES FOR JUNE 1ST AND 2ND. SITE...6/1..............6/2.............. DCA....54 (1907)........53 (1907)........ BWI....54 (1907)........53* (1907)....... IAD....63 (2001/1966)...64 (1974/1963)... *ALSO RECORD DAILY LOW MAXIMUM TEMPERATURE FOR THE MONTH && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM NOON SATURDAY TO 2 AM EDT SUNDAY FOR ANZ530-537>542. SMALL CRAFT ADVISORY FROM 10 AM SATURDAY TO 8 AM EDT SUNDAY FOR ANZ531>534-543. && $$ PRODUCTS...WOODY!/ADS/DFH

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