000
FXUS61 KLWX 100228
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
928 PM EST TUE MAR 9 2010

.SYNOPSIS...
HIGH PRESSURE WILL MOVE OFF THE COAST OVERNIGHT. LOW PRESSURE OVER
THE CENTRAL GREAT PLAINS WILL SLOWLY APPROACH THE REGION THROUGH
THE REST OF THE WORK WEEK...RESULTING IN CLOUDY SKIES AND PERIODS
OF RAIN FROM THURSDAY THROUGH THE WEEKEND.

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
AXIS OF HIPRES RDG PUSHING OFFSHR...AND CI HAS BEEN SPREADING ACRS
SKY. NEAREST LOPRES CNTR STILL BACK NEAR KC /MCI/...BUT BAND OF
WMFNTL RA HAS BEEN EVIDENT ACRS MIDWEST-- THE ERN EXTENT OF WHICH
HAS BEEN BRKG APART AS IT ENCOUNTERS SUPER-DRY AMS OVR MID ATLC
/00Z PWATS FM RGNL RAOBS... PBZ 0.10...LWX 0.14..RNK 0.40/. 18Z
NAM PICKS UP ON THIS BEST... WHILE GFS AND 15Z SREF STILL HOLD
ONTO CHC POPS FOR WRN/NRN SXNS. THERE IS LMTD FORCING ALOFT
/H8-5/...THO F-VCTR CNVGNC AND MSTR DISPLACED FM EACH OTR. HWVR...
DO THINK THAT THERE/S ENUF FOR CLDS TO LWR AND A FEW SPRNKLS WL BE
PSBL. BUT...GOTTA WONDER HOW MUCH OF THIS WL JUST GO TWD MSTNG
AMS INSTEAD. HV TRIMMED POPS BACK TO JUST SCHC TNGT...AND REDUCED
AREAL CVRG AS WELL.

TEMPS AT 01Z STILL RNG FM THE MID 40S TO MID 50S...MILD FOR ELY
MAR. THE ADDED CLRCVR AND MSTR ADVCTN WL SHARPLY IMPEDE RADL
COOLING TNGT. GOING MIN-T FCST APPEARS TO BE REASONABLE...AND ONLY
MINOR MODIFICATIONS MADE.

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
THE WMFNT...AND ZN OF PSBL PCPN...WL BE THE NEMESIS INTO WED MRNG.
SAME ISSUES REMAIN...LGT QPF FALLING INTO DRY AMS. HV DECENT
CONFIDENCE ON A FEW SPRNKLS...SPCLY ACRS MD...BUT HV DOUBTS IF
MEASUREABLE PCPN WL FALL. CONTD TRENDS STARTED IN 1ST PD...CUTTING
BACK TO SCHC POPS A LOT AND TARGETING AREAL CVRG COINCIDENT W/
WMFNT AND CLDS.

THRAFTR...MDL TIME HGTS REVEAL MSTR ARND H7...WHICH GRDLY BRKS
APART DURING THE AFTN. HV PULLED POPS ENTIRELY IN THIS PD /WED AFTN/.
BKN CIGS XPCTD. MAXT WL DEPEND ON EXACTLY HOW MUCH SUN WL BE
REALIZED. HV LEFT GOING TEMP FCST IN PLACE...ALLWG MID SHIFT TO
REVIEW 00Z DATA AND MAKE THE CALL.

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
LOW PRES WL REMAIN OVER THE CENTRAL MS VLLY WED NGT THRU FRI.
INITIAL BEST CHCS FOR RA LOOK TO BE LATE THU/THU NGT AS LOW LVL
WINDS TURN TO THE SE AND TAP INTO ATLC MOISTURE. HV UPPED POPS
TO CAT FOR THU NGT W/ QPF ARND 1/2 INCH. TEMPS TO RANGE FM L40S IN
THE HIGHLANDS TO A50 IN THE CITIES.

HAVE BUMPED UP POPS FRIDAY NIGHT AND SATURDAY. LARGE UPPER-LEVEL LOW
OVER THE CENTRAL CONUS DURING THE MIDDLE PORTION OF THE WEEK WILL
SLOWLY DRIFT TOWARD THE TENNESSEE VALLEY THROUGH SATURDAY. AN
UPPER-LEVEL DISTURBANCE WILL ROTATE AROUND THE LOW CAUSING COASTAL
LOW PRESSURE TO DEVELOP OFF THE SOUTHEAST COAST FRIDAY. THIS LOW
WILL TRACK INTO OUR CWA SATURDAY BEFORE THE SYSTEM EVENTUALLY BECOMES
VERTICALLY STACKED BY SUNDAY. THE LOW-LEVEL FLOW WILL BACK TO THE
SOUTHEAST AHEAD OF THE COASTAL LOW CAUSING COPIOUS AMOUNTS OF
MOISTURE TO STREAM IN FROM THE ATLANTIC OCEAN. THE DYNAMICS
ASSOCIATED WITH THE COASTAL LOW WILL COMBINE WITH THE DEEP MOISTURE
TO BRING RAIN POSSIBLY HEAVY AT TIMES ESPECIALLY FRIDAY NIGHT AND
SATURDAY.

THIS BRINGS UP A MAJOR CONCERN - THAT OF FLD PTNL AS ALL THE RMNG
SNOW IN THE HIGHLANDS BEGINS TO MELT/RELEASE INTO THE N BRNCH OF
THE PTMC. TUESDAYS SNOW WATER EQUIV GRAPHIC FM NOHRSC STILL
SHOWING 5-10 LIQUID EQUIVALENT LOCKED IN THAT SNOWPACK. THE RAIN
THURSDAY NIGHT INTO FRIDAY WILL COMBINE WITH SNOWMELT TO CAUSE
POSSIBLE FLOODING OF SMALL STREAMS AND CREEKS ALONG AND WEST OF
THE ALLEGHENY FRONT THURSDAY NIGHT INTO FRIDAY. HOWEVER...THERE IS
A GREATER CONCERN FOR SIGNIFICANT FLOODING ACROSS THE REST OF THE
AREA OVERNIGHT FRIDAY INTO EARLY NEXT WEEK. THE FIRST THREAT WILL
BE FROM HEAVY RAIN OVERNIGHT FRIDAY THROUGH SATURDAY WHERE SMALL
STREAMS AND CREEKS MAY FLOW OUT OF THERE BANKS. THE OTHER THREAT
WILL BE FROM RIVER FLOODING DURING THE SECOND HALF OF THE WEEKEND
INTO EARLY NEXT WEEK.

LONG-RANGE GUIDANCE SHOW THE UPPER LOW BECOMING NEARLY STATIONARY
AROUND OR JUST OFF THE NEW ENGLAND COAST FOR THE SECOND HALF OF
THE WEEKEND AND POSSIBLY INTO ERY NEXT WEEK. WITH THIS
SETUP...COLDER AIR WILL MOVE INTO THE REGION AND SHOWERY ACTIVITY
WILL LINGER THRU ERY NEXT WEEK. PRECIP MAY BE COLD ENOUGH FOR A
WINTRY MIX ACROSS THE WRN SLOPES OF THE ALLEGHENY FRONT AT NIGHT
SAT THRU MON.

.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
HIGH CLDS SPREADING ACRS TERMINALS THIS EVNG. WMFNT WL CROSS
OVNGT. ATTM...HV KEPT VCSH AND CIGS ARND BKN050 COINCIDENT W/ FNT.
AM HAVING DOUBTS WHETHER ANY RA WL FALL. IF IT DOES...IT/LL BE
JUST SPRNKLS. XPCT NO RESTRICTIONS ASSOC W/ THIS ACTVTY.

MID DECK CLDS AND S/SE WNDS BLO 10 KT WED ONCE WMFNT PASSES. DC-
BALT TERMINALS WL BE CLSR TO ESE...WHILE CHO-MRB WL BE MORE SLY.

UNSETTLED CONDITIONS XPCTD ACROSS THE MID ATLC STATES WED NGT AND
LASTING RIGHT THRU THE WKND. SUB VFR W/ PDS OF RAIN THU THRU SUNDAY.

.MARINE...
SLY FLOW ON THE WATERS THRU WED...AOB 10 KT. NRN BAY NOT QUITE
THERE YET...BUT IT WL BE SOON.

THERE IS PTNL FOR SCA WINDS...ESPECIALLY FRI. THE THING THAT COULD
WORK AGAINST SERLY WINDS MIXING DOWN TO WATER LVL IS THE L40
DEGREE WATER IN THE BAY/PTMC. BUFKIT SNDGS SHOW A NEAR SFC
INVERSION AT NHK W/ XCPTN OF A BRIEF PD DURG AFTN.

.TIDES/COASTAL FLOODING...
ANOTHER CONCERN WL BE CSTL FLD PTNL THIS WKND. THERE ARE MULTIPLE
FACTORS INVOLVED - 1 WATER FLOWING DOWNSTREAM IN THE PTMC 2 MOON
PHASE IS GROWING CLOS TO A NEW MOON SUNDAY 3 LOW PRES MOVING OVER THE
RGN THIS WKND AND 4 LOW LVL SERLY FLOW FRI-SAT WL HINDER DRAINAGE
IN THE PTMC/CHES BAY. THIS TOO IS TOO FAR INTO THE FUTURE TO
WARRANT ANY TYPE OF SPL PRODUCT OTHER THAN TO MENTION IN THE HWO.
LATER SHIFTS WL NEED TO EVALUATE THIS THREAT FURTHER.

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.

SYNOPSIS...
NEAR TERM...HTS
SHORT TERM...HTS
LONG TERM...LASORSA/WOODY
AVIATION...HTS/WOODY
MARINE...HTS/WOODY
TIDES/COASTAL FLOODING...WOODY