Area Forecast Discussion
Issued by NWS Sterling, VA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33
000
FXUS61 KLWX 191331
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
931 AM EDT SAT APR 19 2014

.SYNOPSIS...
HIGH PRESSURE CENTERED OVER ONTARIO WILL BUILD INTO THE NORTHEAST
U.S. THIS AFTERNOON AND TONIGHT. THE HIGH WILL REMAIN IN CONTROL
OF THE REGION`S WEATHER THROUGH MONDAY. A COLD FRONT WILL BRING
SHOWERS TO THE AREA TUESDAY. HIGH PRESSURE WILL RETURN FOR
WEDNESDAY AND THURSDAY...BEFORE ANOTHER COLD FRONT APPROACHES THE
AREA ON FRIDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
13Z VISIBLE SATELLITE IMAGERY SHOWS CIRRUS GRADIENT OVER REGION
WITH SCT-TO-BKN-TO-OVC FROM NORTH-TO-SOUTH. KNHK HAS BKN MID DECK
AND EXPECTING THAT TO SUSTAIN ITSELF IN THE SOUTHERN PART OF THE
MD PORTION OF THE CHESAPEAKE THROUGH MID AFTERNOON. USING GFS
LAYER H5-H3 RH AS A PROXY FOR THE HIGH CLOUDS...EXPECTING ERODING
TREND FOR HIGH CLOUDS FOR THIS AFTERNOON ACROSS MUCH OF THE AREA
EXCEPT EXTREME SOUTHERN MD AND LOWER BAY MARINE ZONE.

NOT EXPECTING PRECIP SHIELD ASSOCIATED WITH RAIN ACROSS SE VA/NC
TO MAKE IT MUCH FURTHER NORTH THAN IT CURRENTLY IS...AS STRONG
ANTICYCLONIC SFC FLOW WILL PREVENT NORTHWARD PUSH. ENTIRE CWA WILL
BE PRECIP FREE TODAY...WITH LIGHT N/NE WIND FLOW.

ADJUSTED TEMPS ALONG THE IMMEDIATE WEST SHORE OF THE CHESAPEAKE
INCLUDING CITY OF BALTIMORE AND ANNAPOLIS AS NE FLOW OVER THE 50F
BAY TO INHIBIT HEATING ABOVE 60F. OTHERWISE...TEMPS ARE EXPECTED
TO HIT MID60S THROUGHOUT CWA DESPITE THE CHILL START OF TODAY.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/...
THE SERN LOW WL MOVE OFFSHORE TNGT...BUT IS NOT XPCTD TO BE A
PLAYER IN MID ATLC WX. AGN HIGH PRES TO THE N WL BE FILTERING IN
TO THE RGN...BRINGING CLR SKIES AND GOOD RAD CONDS. ATTM MDLS ARE
FCSTG A40 BUT FEEL W/ THIS SET UP TEMPS COULD DROP LOWER AWAY FM
THE CITIES. W OF I-95 TEMPS WL FALL INTO THE U30S - IF DAYSHIFT FEELS
TEMPS COULD GO A LTL LOWER A FROST ADVSRY MAY BE NEEDED BUT AM
GOING TO ALLOW THE LATER SHIFT TO MAKE THAT DETERMINATION.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
`TIS THE SEASON FOR CUT-OFF UPPER LOWS. WITH THE JET STREAM
RETREATING SLOWLY TO THE NORTH BUT STILL HANGING AROUND THE
US/CANADA BORDER...ENOUGH ENERGY EXISTS IN THE INCOMING SHORTWAVES
FOR SOME TO `BREAK OFF` AND HOVER FURTHER SOUTH OVER THE CONUS. THE
FIRST ONE IN THE CURRENT FORECAST CYCLE IS THE UPPER LEVEL LOW
SPINNING OFF THE SE ATLC COAST. THIS FEATURE WILL CONTINUE TO SPREAD
RAIN ACROSS THE CAROLINAS INTO SUNDAY AS THE UPPER LOW SLOWLY DRIFTS
OFF THE COAST AHEAD OF THE NEXT SHORTWAVE. HIGH PRESSURE WILL
SQUEEZE IN BETWEEN THESE TWO SYSTEMS...CENTERED OVER NEW ENGLAND AND
STRETCHING DOWN ACROSS THE DEEP SOUTH. THE POSITION OF THE HIGH WILL
CONTINUE TO STREAM IN ONSHORE FLOW TO THE MID-ATLC...KEEPING THE
TEMPS/HUMIDITY MODERATED W/ HIGHS ON SUN ONLY IN THE L/M60S.
RELATIVELY DRY AIR FROM THE ELY FLOW WILL ALLOW TEMPS TO DROP DOWN
INTO THE 40S FOR OVERNIGHT LOWS BUT STILL WELL ABOVE FREEZING.

ON MONDAY...THE SHORTWAVE THAT WAS INITIALLY ASSOCIATED W/ AN UPPER
LOW OVER THE CNTRL PLAINS WILL GET PULLED BACK INTO THE FASTER UPPER
FLOW. BY LATE MON...THE BETTER ORGANIZED SHORTWAVE WILL BE
STRETCHED OUT FROM THE GREAT LAKES TO THE SRN PLAINS WHILE THE MID
ATLC RECEIVES ANOTHER DAY OF REPRIEVE FROM ACTIVE WX. THE ELY
ONSHORE FLOW WILL DROP OFF AND WINDS WILL TURN MORE SLY...ALLOWING
THE WRN HALF OF THE REGION TO WARM-UP INTO THE L70S WHILE THE ERN
HALF ENDS UP A FEW DEGREES COOLER FOR DAYTIME HIGHS. MOST MED RANGE
MEMBERS SHOWING THIS...ESPEC THE GFS. THE BIAS-CORRECTED VERSIONS OF
BOTH THE GFS AND NAM ARE BOTH A FEW DEG WARMER OVERALL THAN THEIR
DETERMINISTIC PARENT - SO MORE OF A BLEND WAS UTILIZED.

A DECENT COLD AIR ADVECTION REGION WILL BE PUSHING THE SHORTWAVE
FROM THE OHIO VLY TOWARD THE APLCNS EARLY TUE. THE SFC LOW WILL GAIN
SOME STRENGTH ON TUE AS IT MOVES ACROSS THE ERN GREAT LAKES...BUT
TAKE A GOOD PORTION OF THE DYNAMICS W/ IT TO THE NORTHEAST - AT
LEAST INITIALLY. THOUGH THE NAM`S CURRENT CYCLE ENDS EARLY
TUE...COMPARING THE APPROACH OF THE SHORTWAVE AND SFC FEATURES TO
THE GFS AND EURO SHOWS A WEAKER FEATURE THAN EITHER LONG RANGE
MEMBER BUT CLOSER TO THE EURO. THE 00Z GFS BRINGS A KICKER DOWN
ACROSS THE REGION LATE TUE INTO EARLY WED...BUT JUST AFTER A BULK OF
THE PRECIP HAS EXITED. THE 00Z EURO IS A BIT SLOWER W/ THE
PROGRESSION AND EXIT OF THESE FEATURES...WHICH BRINGS INTO QUESTION
THE POTENTIAL FOR CONVECTION ALONG W/ THE FRONTAL PASSAGE ON TUE
AFTN/EVE. MODEL SOUNDINGS ONLY PAINTING A LOW/MODEST AMOUNT OF
FAVORABLE CONVECTIVE PARAMETERS ACROSS THE SRN TIER OF THE CWA WHICH
TAPERS OFF SUBSTANTIALLY TOWARD THE I-66 OF NRN VA. ENOUGH WARM AIR
AND EXPECTED HIGHS IN THE L-M70S FOR THESE SRN TIER AREAS FOR AT
LEAST A CHANCE FOR ELEVATED OR BRIEF CONVECTIVE INITIATION - SO A
SLIGHT CHANCE OF THUNDER INTRODUCED FOR THE BRIEF FEW HRS OF TUE
AFTN/EVE.

A MODEST REGION OF SUBSIDENCE WILL THEN SPREAD ACROSS THE AREA ON
WED...BRINGING GUSTY NW WINDS AND DRIER/COOLER AIR. NOT NEARLY AS
POTENT AS THE STORM SYSTEM A WEEK AGO AT THE SAME TIME...BUT STILL
ONLY ALLOWING TEMPS TO RISE BARELY INTO THE L60S ACROSS MUCH OF THE
AREA W/ A BRISK 15-25MPH NW WIND. A POTENT CUT-OFF UPPER LOW OVER
THE NRN ROCKIES WILL LOSE SOME OF ITS PUNCH AS IT SLIDES EAST OF THE
MISS RVR LATE THIS WEEK...AS HIGH PRESSURE AGAIN GIVES THE MID ATLC
A COUPLE MORE QUIET WX DAYS FOR THU AND FRI.

&&

.AVIATION /13Z SATURDAY THROUGH WEDNESDAY/...
VFR CONDS XPCTD TDA AND TNGT.

ONSHORE WINDS WILL CONTINUE ON SUNDAY...W/ A STEADY 10-15KT BREEZE
EXPECTED BUT THE NEXT CHANCE FOR PRECIP WILL HOLD OFF UNTIL TUE
AFTN/EVE W/ A COLD FRONTAL PASSAGE. A CHANCE FOR A FEW TSTMS SOUTH
OF THE DC METRO AREA TAF SITES W/ THE BOUNDARY...THEN THIS ACTIVITY
WILL PUSH OFF THE COAST INTO THE LATE NIGHT HRS. HIGH PRESSURE AND
SOME GUSTY NW WINDS ON WED...W/ MORE QUIET WX ON THU AND FRI.

&&

.MARINE...
HAVE INTRODUCED A SCA FOR THE LOWEST MARINE SEGMENTS FOR THE
PERIOD OF PEAK SOLAR HEATING THIS AFTERNOON 2PM TO 6PM ...AS BOTH
THE NAM AND GFS HAS MEAN 15-20KTS WIND IN THE LAYER 975 TO 925 MB.

THERE WILL BE A LULL IN THE SCA UNTIL LATER TONIGHT...WHEN THE
SAME AREA WILL SEE SCA CONDITIONS ONCE AGAIN AS THE SFC PRESSURE
GRADIENT INCREASES AS HIGH MOVES OVER CAPE COD...COUPLED WITH THE
SFC LOW OVER THE SE US COAST.

HIGH PRESSURE WILL HANG TIGHT OVER NEW ENGLAND AND INTO THE MID ATLC
REGION ON SUN...THOUGH THE INCREASING PRES GRADIENT OVER DELMARVA
WILL ALLOW THE ELY FLOW TO RISE JUST INTO SCA RANGE FOR MUCH OF THE
MD BAY FROM THE PREDAWN HRS SUN THRU LATE EVE. WINDS WILL THEN SLACK
OFF FOR THE OVERNIGHT HRS AS THE HIGH MOVES OFF THE COAST AND WINDS
TURN SLY. A COLD FRONT WILL PUSH THRU THE REGION LATE TUE...BRINGING
SOME SCATTERED SHOWERS AND POSSIBLY SOME ISOLATED TSTMS JUST SOUTH
OF THE METRO DC AREA. BREEZY NW WINDS OF WED AFTN...THOUGH HIGH
PRESSURE WILL AGAIN OVERTAKE THE REGION FOR THE SECOND HALF OF THE
WEEK.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 10 AM TO 6 PM EDT SUNDAY FOR
     ANZ531>533-538>542.
     SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 6 PM EDT THIS
     EVENING FOR ANZ534-537-543.
     SMALL CRAFT ADVISORY FROM 4 AM TO 6 PM EDT SUNDAY FOR ANZ534-
     537-543.

&&

$$
SYNOPSIS...LEE
NEAR TERM...LEE
SHORT TERM...GMS/ABW
LONG TERM...GMS/ABW
AVIATION...GMS/ABW
MARINE...LEE/GMS/ABW







USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.