FXUS61 KLWX 042007
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
307 PM EST SAT FEB 4 2012

.SYNOPSIS...
LOW PRESSURE WILL MOVE EAST ACROSS THE CAROLINAS INTO SUNDAY AS A 
COLD FRONT DRIFTS SOUTH ACROSS THE CENTRAL MID ATLANTIC. HIGH 
PRESSURE WILL BUILD FROM THE NORTHWEST SUNDAY NIGHT THROUGH MONDAY 
NIGHT AS AN UPPER TROUGH MOVES EAST ACROSS THE SOUTHERN MID 
ATLANTIC. A WEDGE OF HIGH PRESSURE THEN DEVELOPS TUESDAY NIGHT 
THROUGH WEDNESDAY WHILE AN UPPER TROUGH BRINGS ANOTHER WINTRY MIX TO 
THE REGION.

.NEAR TERM /THROUGH SUNDAY/...
QSTNRY SFC FNT ACRS SRN CWFA ATTM...STRETCHING BACK TWD LOPRES NEAR 
PAH. A CDFNT EXTENDS SWD FROM LOW TWD GULF CST. VIGOROUS TSTM 
ACTIVITY EVIDENT ACRS LA/MS/ARK ALL DAY...WHICH SHUD PLAY A ROLE IN 
LIMITING NWD EXTENT OF MSTR. THE UPR LOW CAN BE SEEN ON VAPOR LOOP 
OVER THE CENTRAL PLAINS. FURTHER...THERE/S A BAND OF PCPN ACRS SRN 
PA...WHICH CORRELATES WITH H8 FNT/MID-LVL F-VECTOR CNVGNC. WAA 
INDUCED PCPN CAN BE SEEN CLOSING IN FM THE W/SW. AS SUSPECTED...CLDY 
SKIES ALL DAY HV LIMITED TEMPS...AND THAT HAS COMBINED WITH EVAP 
COOLING TO PERMIT PCPN IN THE BAND TO FALL AS SNOW IN SPOTS. 
HWVR...ITS BEEN TOO WARM FOR ACCUMS...FOR NOW.

ALL WX SYSTEMS HV BEEN MVG EWD...AND WL CONT TO DO SO TNGT...GUIDED 
BY NRN STREAM S/WV. THAT WAVE WL ALSO INHIBIT TRUE COLD AIR FM 
DRAINING SWD. THUS...WL ONLY HV DIURNAL AND EVAP EFFECTS FOR 
SYNOPTIC SCALE COOLING. ADDTL DYNAMIC COOLING WL COME INVOF BAND OF 
FGEN FORCING. THAT BAND AND WAA ARE THE TWO SOURCE RGNS FOR PCPN. 
NEITHER WUD BE BIG QPF PRODUCERS. 

12Z GDNC...LED BY THE GFS...HV BACKED OFF ON OVERALL PCPN POTL. NAM 
QPF LOOKS OVERDONE FOR THE SIUTATION...UNLESS GLFMEX MSTR DOES 
MANAGE TO MAKE IT N INTO PA. THAT DOES NOT APPEAR LKLY. THEREFORE... 
PRIMARY CONCERN TURNS TO THE FGEN BAND DROPPING SWD. ASSOC DEEP LYR 
MSTR BGNG TO AFFECT NRN MD ATTM...AND WL BE A CONSIDERATION IN THE 
PTMC HIGHLANDS/NRN SHEN VLY/N OF DC/METRO BALT FOR THE EVNG HRS. 
BASED ON TIMING AND OBSVD WX...HAD TO LEAN A BIT MORE ON SNW FOR 
PTYPE. STILL A BIT UNCERTAIN IN THAT ELEMENT...BUT REAL-TIME OBS 
ADDING CONFIDENCE. SNW ACCUM MINIMAL. SUBFRZG TEMPS MOST LKLY W OF 
FDK...WHERE UP TO AN INCH PSBL. 

BAND OF FORCING DROPS S OF DC OVNGT WHERE TEMPS WL HV A GREATER INFL 
FM WAA...SO SNW /SPCLY ACCUMS/ EVEN MORE IFFY. DP LYR MSTR WL BE 
GONE BY THE TIME MARGINALLY COLD AIR ARRIVES. AM CUTTING BACK ON 
POPS AS RASN MIX BECOMES MORE EXPANSIVE IN WX GRIDS.

MSTR FM SRN STREAM SYSTEM WL BE GONE BY SUN MRNG. WL TURN ATTN TWD 
PVA FM NRN STREAM FOR ANY PCPN POTL. WL HOLD ONTO CHC POPS... 
PRIMARILY IN THE MRNG. BINOVC SHUD BE MORE NMRS IN THE AFTN. 
PREFERRED COOLER MAV MAXT AS MILD CAA SHUD PREVAIL...BUT THERE/S 
ISNT AN INFLUX OF TRUE COLD AIR BHD THIS SYSTEM.

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
SUNDAY NIGHT THROUGH MONDAY...A WEAK REMNANT OF THE UPPER LOW 
CURRENTLY OVER THE CENTRAL GREAT PLAINS LOOKS TO MOVE EAST ACROSS NC 
AS A SFC RIDGE PERSISTS ACROSS THE NRN AND CNTRL MID ATLANTIC 
STATES. WITH CLOUDS SHUNTED MAINLY SOUTH OF THE LWX CWA...EXPECT MID 
TO UPR 20 MIN TEMPS INLAND...WITH LOW TO MID 30S FOR URBAN/NEAR 
SHORE. A WLY COMPONENT TO THE WIND /GFS HAS STRAIGHT WEST WITH 
LITTLE SFC REFLECTION OF UPR LOW TO THE SOUTH WHILE ECMWF HAS A SWLY 
SFC FLOW DUE TO THE LOW/ WILL DOWNSLOPE AND WARM...MAX TEMPS AROUND 
50F AT LOWER ELEVATIONS.

MONDAY NIGHT THROUGH TUESDAY...SFC HIGH STRENGTHENS FROM THE 
NORTH...WITH OVERNIGHT MIXING FROM NWLY FLOW KEEPING MIN TEMPS TO 
AROUND 30F INLAND...LOW TO MID 30S AGAIN URBAN/NEAR SHORE. SUNNY 
START TO TUESDAY...WITH HIGH CLOUDS THICKENING THROUGH THE AFTERNOON 
AHEAD OF A SHORTWAVE TROUGH APPROACHING FROM THE CENTRAL CONUS. MILD 
TEMPERATURES WITH DOWNSLOPING NWLY FLOW...MAX TEMPS LOW TO MID 
50S SOUTH...UPR 40S TO 50F NORTH. 

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
HIGH PRESSURE CENTER SHIFTS EAST ACROSS THE NORTHERN MID 
ATLANTIC/NEW ENGLAND TUESDAY NIGHT THROUGH WEDNESDAY...SHIFTING A 
NLY FLOW TO NELY/ONSHORE. MEANWHILE...A SHORTWAVE TROUGH CROSSES THE 
REGION PROVIDING LIFT FOR SOME WINTRY PRECIPITATION /GENERALLY NORTH 
AND WEST OF BALT-WASH AS USUAL/. STILL UNCERTAINTY WITH TIMING /GFS 
12 HOURS AHEAD OF THE ECMWF/ AND LOCATION...SO WENT FOR JUST CHANCE 
POPS WED/WED NIGHT.

HIGH PRESSURE TO END THE WEEK.

.AVIATION /20Z SATURDAY THROUGH THURSDAY/...
RAIN AND SNOW SHOWERS STRETCHED ALONG MASON-DIXON LINE WILL SLOWLY 
DRIFT SOUTH INTO NORTHERN MD AND THE WV PANHANDLE.  OVERALL 
PROJECTION OF SHOWERS IS WEST TO EAST SO IMPACT ON TERMINALS WILL 
SLOWLY INCREASE OVER THE NEXT FEW HOURS.  CEILINGS ARE EXPECTED TO 
LOWER TO MVFR LATE THIS AFTERNOON FOR MRB-IAD-BWI-MTN.  SHOWERS WILL 
TURN FROM RAIN TO RAIN-SNOW BY MIDNIGHT TONIGHT AT THOSE TERMINALS.  
NORTHERN TERMINALS INCLUDING MRB AND BWI-MTN HAVE BEST CHANCE TO SEE 
REDUCED VISBYS DUE TO ALL SNOW FOR A FEW HOURS OVERNIGHT AND INTO 
SUNDAY MORNING.  IFR CONDITIONS POSSIBLE DURING THIS TIME.  MOISTURE 
FROM THE SOUTH WILL CONTINUE TO MOVE NORTH AS WELL AND REDUCE VISBYS 
AND CEILINGS AT CHO.  CONFIDENCE IS CURRENTLY LOW ON RAIN-SNOW LINE 
AS IT SINKS INTO THE MID ATLANTIC REGION.  DCA IS CURRENTLY EXPECTED 
TO STAY ALL RAIN THROUGH THE PERIOD. 

VFR SUNDAY NIGHT THROUGH PROBABLY TUESDAY UNDER HIGH PRESSURE ACROSS 
THE AREA /AND A WEAK LOW CROSSING NORTH CAROLINA MONDAY/. LIGHT NLY 
FLOW TURNS WLY FOR MONDAY. A WEDGE OF HIGH PRESSURE TUESDAY NIGHT 
THROUGH WEDNESDAY WITH IFR POSSIBLE BY WEDNESDAY.

.MARINE...
FNT JUST S OF THE WATERS...PERMITTING N/NELY FLOW. HWVR...MIXING 
POTL NOT THAT GREAT...AND WNDS HV BEEN AOB 10 KT. THOSE SPDS SHUD 
PREVAIL THRU THE NGT. MOMENTUM TRANSFER SHUD BE INTERRUPTED FURTHER 
BY PENDING PCPN. 

MSTR PUSHES S OF WATER TMRW MRNG...FLLWD BY S/WV PASSAGE DURING THE 
MIDDAY. FLOW BACKS NWLY BHD TROF. THAT/S WHERE THERE SHUD BE IMPRVD 
MIXING...BUT THE P-GRAD REMAINS WEAK. HV OPTED TO KEEP ALL WINDS AND 
GUSTS UNDER SCA THRESHOLDS.

NLY FLOW 10 TO 15 KT SUNDAY EVENING...EASING THROUGH THE NIGHT AND 
BECOMING WLY THROUGH MONDAY. MORE NLY FLOW TUESDAY...BECOMING NELY 
TO ELY TUESDAY NIGHT AND WEDNESDAY AS A WEDGE OF HIGH PRESSURE 
BUILDS FROM THE NORTHEAST. NO HEADLINES ANTICIPATED THROUGH MIDWEEK.

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

SYNOPSIS...JACKSON
NEAR TERM...HTS
SHORT TERM...JACKSON
LONG TERM...JACKSON
AVIATION...HAS/JACKSON
MARINE...HTS/JACKSON