Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 210131
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
931 PM EDT MON APR 20 2015

.SYNOPSIS...
A COLD FRONT WILL PUSH EAST ACROSS THE REGION DURING THE OVERNIGHT
HOURS. AN UPPER LOW WILL THEN PERSIST ACROSS THE GREAT LAKES TO
NEW ENGLAND THROUGHOUT THE WEEK.

&&

.NEAR TERM /THROUGH TUESDAY/...
TORNADO WATCH REMAINS IN EFFECT FOR THE ENTIRE AREA THROUGH 10 PM.

01Z ON GOING TSTM ACTIVITY WITH SCT SVR TSTMS...MAINLY OVER
EASTERN AREAS. COLD FRONT CURRENTLY POSITIONED BACK ACROSS
WV...WITH A WARM FRONT STILL NEAR THE MASON-DIXON LINE. LATEST
MESO RUNS SHOWING SCT ACTIVITY WILL CONTINUE UNTIL FRONTAL
PASSAGE...BETWEEN 04 AND 07Z. SEVERE THREAT WILL DIMINISH HERE IN
THE NEXT 1-2 HRS WITH LOSS OF DAYTIME HEATING ALONG WITH A WORKED
OVER ENVIRONMENT FROM THE EARLIER STORMS. THERE AFTER EXPECTING
MAINLY SHOWERS...WITH PERIODS OF HEAVIER RAIN PSBL. LATEST WATER
VAPOR IMAGERY SHOWING GOOD AMT OF DRIER AIR IN THE WAKE OF THE
FRONT...SO EXPECTING PCPN TO END WITH FRONTAL PASSAGE.

DP UPR LOW WL RESIDE NORTH OF THE GRTLKS TMRW...WHICH WL PROVIDE
FAST MID-LVL FLOW. KEEPING A DRY FCST W/ CLDY PERIODS AS IMPULSES
ZIP THRU THE FLOW. DOWNSLOPING WL PROVIDE THE WARMING IN SPITE OF
CAA.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
NOT MUCH OF A BREAK BETWEEN SYSTEMS AS THE MID-ATLC STAYS JUST ON
THE OUTER FRINGE OF A LARGE UPPER GREAT LAKES TROUGH. ONE OF THE
WEAKER VORTS SLIDING AROUND THE BASE OF THE TROUGH WILL SLIDE INTO
THE WINDWARD SIDE OF THE APLCNS LATE TUE NIGHT. LITTLE MORE THAN
COOLER AIR WILL MAKE IT OVER THE MTNS...W/ THE MOISTURE DISSIPATING
OVER THE HIGHER TERRAIN. HEADING INTO EARLY WED...A STRONGER LOW
PRESSURE SYSTEM WILL BE DEVELOPING WELL TO OUR NORTH WHICH WILL ALSO
STRENGTHEN THE INCOMING COLD FRONT.

GUSTY SW WINDS WILL ARRIVE BEFORE ANY PRECIP E OF THE APLCNS...AND
GRADUALLY PULL UP OUR COOL TEMPS FROM OVERNIGHT BACK INTO A WARMER
REGIME BY MIDDAY. UNLIKE TODAY`S CONDITIONS...THIS FRONTAL PASSAGE
IS NOT EXPECTED TO MUSTER UP MUCH INSTABILITY. THE SRN HALF OF THE
CWA MAY SEE SOME WEAK CONVECTIVE POTENTIAL BUT THE REMAINDER OF THE
AREA WILL SEE AT SOLID CHANCE FOR RAIN SHOWERS. TEMPS WILL BE ABOVE
AVG FOR THE VA/MD PIEDMONT. QPF FAIRLY LIGHT FOR THIS PASSAGE AND A
RELATIVELY BRIEF PERIOD OF THE MID AFTN TO EVE. BY LATE EVE...MOST
OF THE PRECIP WILL BE SLIDING OUT OF THE SE PORTION OF THE CWA AND
CLOUDS WILL ALLOW EXIT OFF THE COAST.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
LONG TERM PERIOD WILL BE DOMINATED BY A COLD UPPER-LEVEL LOW
PRESSURE SYSTEM STALLED OVER THE NORTHEASTERN CONUS...WITH
PERSISTENT CHILLY WEST OR NORTHWEST FLOW OVER THE REGION.

A TROUGH MAY BRING PRECIPITATION TO THE AREA SATURDAY...BUT OTHER
THAN THAT IT LOOKS MAINLY DRY. TEMPERATURES WILL BE WELL BELOW
NORMAL /I.E. 10-15 DEGREES BELOW NORMAL/ THROUGH THE PERIOD WITH
HIGH STRUGGLING TO GET OUT OF THE 50S AND LOWS IN THE UPPER 30S TO
40S.

&&

.AVIATION /01Z TUESDAY THROUGH SATURDAY/...
MAINLY VFR CONDITIONS THROUGH THE TAF PERIOD. ISO SHOWER/TSTM
STILL PSBL THRU 07Z AS COLD FRONT MOVES THROUGH...WITH DRY
CONDITIONS THERE AFTER. ANY TSTM COULD PRODUCE A GUST UP TO 35 KT.
OUTSIDE OF PCPN...WINDS MAINLY SLY AROUND 10 KTS...BCMG WLY LATE
TONIGHT. WIND SHIFT COULD BE DIFFERENT 1-2 HRS.

WLY WINDS OVNGT THRU TUE...W/ GUSTS UP TO 25 KT DURING THE DAY.

ANOTHER COLD FRONT WILL SWING THRU ON WED AFTN. GUSTY SW WINDS AHEAD
OF THE FRONT AND MAINLY BRIEF/SCTD SHOWER ALONG THE BOUNDARY AS IT
SLIDE THRU DURING THE 2ND HALF OF THE DAY.

WLY FLOW 10 KT OR SO W/ MAINLY VFR EXPECTED THU-SAT.

&&

.MARINE...
SCA REMAINS IN EFFECT FOR ALL WATERS...WITH THE UPPER TIDAL
POTOAMC ENDING AFTR 05Z. GUSTS INCREASE AGAIN AFTR DAYBREAK
TUES...SO SCA WILL BE BACK IN EFFECT FOR UPPER TIDAL
POTOMAC...ALONG WITH THE REMAINING WATERS.

SOLID SCA WINDS POSSIBLE ON WED AHEAD OF AND ALONG A COLD FRONT THAT
IS EXPECTED TO SWING THRU THE WATERS BY LATE EVE.

SCA GUSTS POSSIBLE IN WLY SURGE BEHIND FRONTAL BOUNDARY
THURSDAY...THEN LIGHTER FLOW BELOW SCA CRITERIA LIKELY FRIDAY-
SATURDAY.

&&

.TIDES/COASTAL FLOODING...
WATER LEVELS STILL BETWEEN 1.5 AND 2.0 FT ABV ASTRO NORMS. AT THIS
RATE...WILL HAVE MINOR FLOODING AT ANNAPOLIS AND BALTIMORE. SLY
FLOW WILL REINFORCE THE POSITIVE DEPARTURES. HOWEVER...A COLD
FRONT WILL BE APPROACHING...SWINGING AROUND WIND DIRECTION RIGHT
NEAR THE TIME OF HIGH TIDE. THAT MAKES IT LOWER CONFIDENCE...BUT
STILL OPTED TO ISSUE ADVY. WILL CONTINUE TO MONITOR.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...COASTAL FLOOD ADVISORY UNTIL 11 PM EDT THIS EVENING FOR MDZ011-
     014.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT TUESDAY FOR ANZ530>534-
     537>543.
     SMALL CRAFT ADVISORY UNTIL 1 AM EDT TUESDAY FOR ANZ535-536.
     SMALL CRAFT ADVISORY FROM 10 AM TO 6 PM EDT TUESDAY FOR ANZ535-
     536.

&&

$$



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