019 FXUS61 KLWX 201426 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE/WASHINGTON 1030 AM EDT SAT JUL 20 2002 DIFFUSE...WEAKENING CDFNT OVR THE AREA THIS MORNING BUT ITS TOUGH TO PLACE THE EXACT LOCATION OF THE FNT. WINDS HAVE GONE N OVR MUCH OF THE AREA IMPLYING THE FNT IS TO OUR S. HOWEVER...MSAS ANALYSIS SHOWS DWPTS STILL RUNNING HIGH AND NEG LIS OVR MUCH OF THE CWA. LWR DWPTS AND MORE STABLE AIR REMAINS OVR PA. SOME OF THE SLIGHTLY DRIER AND SLIGHTLY MORE STABLE AIR SHOULD WORK ITS WAY SWD INTO THE AREA DURING THE AFTERNOON. CANT RULE OUT A SHRA NEXT COUPLE OF HOURS ACRS THE NRN ZNS GIVEN INSTABILITY BUT CHC WILL DECREASE BY AFTERNOON SO WILL NOT MENTION PCPN NRN 2/3 OF AREA. ACRS THE SRN 1/3 OF THE AREA...AIR MASS WILL REMAIN MORE UNSTABLE INTO THE AFTRN AND DWPTS WILL BE HIGHEST IN THAT AREA. THIS COMBINED WITH THE PROXIMITY OF THE WEAKENING FRONT WARRANTS A 30 POP FOR THE AFTRN FOR THAT AREA. PLENTY OF CLOUDS ACRS THE AREA THIS MORNING. THINK MORE BINOVC WILL FORM AS THE AFTRN PROGRESSES SO WILL HOLD ONTO THE P/C FCST. CLOUDS HAVE KEPT TEMPS FROM RISING RAPIDLY THIS MORNING. 12Z IAD SOUNDING GIVES A MAX OF ONLY 85F. MOST GUIDANCE GIVES US UPR 80S. 12Z MESOETA COMING IN NOW GIVES MUCH OF THE AREA UPR 80S EXCEPT AROUND 90 DCA/BWI CORRIDOR. WILL BACK DOWN TO AROUND 90 IN THE DCA/BWI AREAS AND LEAVE REMAINDER OF TEMPS ALONE. NO CHGS 2ND PD OR BEYOND. WALSTON PREVIOUS AFD BELOW... --------------------------------------------------------------- TDY THRU SUN... SCT SHRAS/TSRAS HV BN OCCURRING ALG H5 VORT LOBE OVR WV THIS AM. CONVECTION ALSO BEING AIDED BY WK CDFNT THAT MOVED S INTO THE FA ERLIER THIS MORNING. VORT LOBE WL PROGRESS E THRU SRN FA THRU ERLY THIS AFTN. RIDGING ALOFT WL BLD OVR THE AREA BHND DEPARTG S/W TROF TNGT AND SUN. DEEP MOISTURE PROGGED TO SHIFT S OF THE FA DUR THE MORNING. MDL X-SECTS SUGGEST SOME RESIDUAL LOW LVL RH WL RMN OVR THE RGN DUR THE AFTN. BEST CHC FOR PCPN WL BE OVR SW ZONES NEAR VORT LOBE DUR THE MORNING. THUS WL HV 30 POP FOR AM SHRAS/TSRAS SW AND GO P/C ELSWHERE. H85 TEMPS WL BE SIMILAR TO WHAT THEY WERE YEST RESULTING IN SIMILAR MAX TEMPS TDY OF ARND 90 DEGS. LOW LVL E GRADIENT WL BE OVR RGN TNGT AS SFC HIGH PRES MOVS E THRU NY/PA AND WAVE OF LOW PRES MOVS E ALG FRONTAL BDRY TO S OF FA. THIS FLOW OFF ATLC WL KEEP SOME RH OVR RGN TNGT SO WL GO P/C. GUIDANCE TEMPS LUK RSNBL. WL CONT M/S FCST FOR SUN DESPITE FAIR AMT OF LOW LVL RH ON MDL X-SECTS. MDLS APPR TO BE RETURNING THE LOW LVL MOISTURE TOO QUICKLY TO THE FA. WENT A FEW DEGS ABV MOS TEMPS AS WAA WL BE OVR RGN. ARTHUR SUN NGT THRU FRI... MED RANGE MDLS IN VERY GOOD AGREEMENT THIS MORN WITH THE 00Z AVN AND 19/1200Z ECMWF PAINTING VERY SIMILAR PICTURES WITH GOOD RUN TO RUN CONSISTENCY. UPR RIDGING WL HOLD OVR THE MID ATL THRU MON...AND WITH WK SUBSIDENCE AND A LACK OF SFC CNVGC WL KEEP POPS AOB 20 SUN-MON NGT. AS RETURN FLOW BECOMES BETTER ESTABLISHED...MORE UNCOMFORTABLE AIRMASS RETURNS TO THE MID ATL FOR MON. ANOTHER CDFNT WL START TO APCH THE AREA FM THE NW DURING THE DAY ON TUE PASSING THRU THE CWA TUE AND STALLING OVER THE DELMARVA BY WED NGT. WL KEEP CHC POPS FOR TUE AFTN RIGHT THROUGH WED. THIS CDFNT TO BE ACCOMPANIED BY DECENT UPR SUPPORT TUE NGT/EARLY WED...AND COULD SEE ORGANIZED CONVECTION ASSOCIATED WITH FROPA. INSTAB WL BE PLENTIFUL...LTL CINH...GOOD CNVGC ALG CDNT...AND LENGTHENING HODOGRAPHS. HOW MUCH RESIDUAL MOISTURE AND ANY PCPN IS HIGHLY DEPENDENT ON WHERE THE CDFNT STALLS OUT...AND HIGHER POPS MAY NEED TO BE CONSIDERED FOR THU. PLAN ON KEEPING THE FCST FOR THU DRY FOR NOW WITH 20 POPS. TEMPS APPEAR TO BE ON TRACK ATTM...AND HV MADE ONLY A FEW TWEAKS FOR NOW. SEASONABLE WX TO END THE WK ACROSS THE MID ATL. THE REST OF THE EXTENDED LOOKS GOOD AND NO OTHER CHGS ATTM. MANNING .LWX... DC...NONE. MD...NONE. VA...NONE. WV...NONE.