Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 290143 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 843 PM EST FRI NOV 28 2014 .SYNOPSIS... HIGH PRESSURE WILL MOVE EAST ACROSS THE AREA TONIGHT. A SOUTHERLY FLOW WILL USHER IN MILDER CONDITIONS FOR THE WEEKEND. A COLD FRONT WILL PASS THROUGH THE AREA MONDAY WITH HIGH PRESSURE BUILDING BACK IN FOR THE MIDDLE OF THE WEEK. && .NEAR TERM /THROUGH SATURDAY/... UPPR LVL TROUGH CONTINUING TO PUSH OFF TO THE NORTH AND EAST TONIGHT WITH NEAR ZONAL FLOW EXPECTED BY SATURDAY MORNING. ATTENTION THIS EVENING IS THE PSBL VERY LIGHT SNOW DEVELOPMENT...MAINLY OVER WESTERN AND CENTRAL MD AND NE WV. 01Z WATER VAPOR IMAGERY INDICATING SHORTWAVE RIDING THE FLOW ALOFT PASSING THROUGH OH AND EVENTUALLY THROUGH CENTRAL PA. OBS AND RADAR REFLECTIVITY WITH THIS ENERGY CURRENTLY REPORTING LIGHT SNOW. QUESTION THOUGH ON HOW INTACT IT REMAINS AS IT NEARS THE CWA. HIGH PRESSURE BUILDING IN AT THE SURFACE HAS USHERED IN MUCH DRIER AIR...WITH DEW PT DEPRESSIONS ANYWHERE 10-15 DEGREES. THE DRIER AIR IN PLACE HAS THUS FAR KEPT ANY OF THE PCPN FRO MAKING IT MUCH FARTHER THAN CENTRAL WV. MESO MODELS SUGGESTIVE OF THIS TREND AND WITH THE PCPN STAYING TO THE NORTH WHERE THE BETTER FORCING IS. HOWEVER...AS THE HIGH NUDGES EAST...SOUTHERLY FLOW RETURNS WHICH MIGHT INJECT IN JUST ENOUGH MOISTURE THAT COMBINING WITH THE ENERGY ALOFT COULD PRODUCE LIGHT SNOW. HAVE GONE WITH MAINLY A DRY FORECAST FOR THE FIRST HALF OF THE NIGHT...WITH SLIGHT CHC POPS FOR THE SECOND HALF RIGHT ALONG THE MASON-DIXON LINE. SOME CLEARING TONIGHT WITH A QUICK DECREASE IN WINDS HAVE ALLOWED MANY AREAS TO ALREADY DROP TO BELOW NORMAL TEMPS. TEMPS WILL MODERATE MORE FOR THE LATTER HALF OF THE NIGHT AS MID LVL CLOUDS MOVE IN WITH SHORTWAVE ALONG WITH WAA WITH THE RETURN FLOW. BY SATURDAY MORNING...THE SHORTWAVE ENERGY WILL BE MORE FOCUSED TO OUR NORTH. THEREFORE...ANY LIGHT SNOW OR FLURRIES EARLY WILL DISSIPATE BY MID MORNING. A SOUTHERLY FLOW BEHIND THE DEPARTING HIGH PRESSURE OVER THE ATLANTIC OCEAN WILL COMBINE WITH SOME SUNSHINE TO BRING MILDER CONDITIONS COMPARED TO RECENT DAYS. HOWEVER...THERE WILL BE BROKEN DECK OF MID-LEVEL CLOUDS OVERHEAD KEEPING MAX TEMPS BELOW CLIMO. MAX TEMPS ARE FORECAST TO RANGE FROM NEAR 40 ALONG THE MASON-DIXON LINE TO THE UPPER 40S IN PORTIONS OF CENTRAL VIRGINIA. && .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... BROAD RIDGING OVER THE ERN CONUS SATURDAY NIGHT THROUGH SUNDAY NIGHT WITH A WARMING TREND BRINGING TEMPERATURES ABOVE NORMAL. WARM AIR ADVECTION WILL SET UP A PERSISTENT CLOUD LAYER IN THE LOWER MID-LEVEL INVERSION. ALMOST ALL PRECIP IS EXPECTED TO BE OVER THE ERN MIDWEST TO THE ALLEGHENY FRONT. FORCING WEST OF THE AREA TURNS TO CONVERGENCE LATE SUNDAY AS A COLD FRONT APPROACHES FROM THE GREAT LAKES. PRECIP EXPECTED TO BE RAIN THROUGH THE EVENT AS THERMAL PROFILES EXCEED FREEZING BELOW 800MB OR SO. DRY EAST OF THE ALLEGHENY FRONT WITH SWLY/SLY FLOW 10 TO 15 MPH MAINTAINED THROUGH SATURDAY NIGHT IN DECENT PRESSURE GRADIENT. LAST DAY OF NOVEMBER WILL HAVE SWLY FLOW AND ABOVE NORMAL TEMPERATURES MID TO UPR 50S FOR MOST INLAND AREAS...LOW 60S POSSIBLE IN THE SWRN HALF OF THE CWA WHERE CLOUD COVER LOOKS TO BE MORE SCATTERED. COLD FRONT APPROACHES FROM THE WEST SUNDAY NIGHT. && .LONG TERM /MONDAY THROUGH FRIDAY/... A COLD FRONT WILL SINK THROUGH THE AREA LATE MONDAY. THERE IS NOT A LOT OF MOISTURE WITH THIS FRONT AND MOST MODELS ONLY HAVE SCATTERED SHOWERS. AS SUCH HAVE CAPPED POPS AT CHANCE MONDAY INTO MONDAY NIGHT. ANY RESIDUAL MOISTURE COULD RESULT IN UPSLOPE SNOW SHOWERS ALONG THE WESTERN RIDGES OVERNIGHT MONDAY NIGHT AS THE COLUMN COOLS. STRONG AND COLD HIGH PRESSURE MOVES BY TO THE NORTH TUESDAY INTO TUESDAY NIGHT. SOUTHERLY RETURN FLOW/ISENTROPIC LIFT SETS UP AS THE AFOREMENTIONED FRONT /WHICH WILL HAVE STALLED TO THE SOUTH/ RETURNS NORTH AS A WARM FRONT. AT LEAST LIGHT PRECIPITATION SEEMS PLAUSIBLE IN THIS SETUP SO HAVE CHANCE POPS TUESDAY NIGHT AS WELL. KEPT IT AS A GENERIC RAIN/SNOW MIX BUT OTHER PTYPES MAY COME INTO PLAY AS WELL AS STRONG COLD AIR DAMMING SIGNATURE IS EVIDENT WHILE WARM AIR OVERRUNS THE COLD AIR AT THE SURFACE. WARMING TREND CONTINUES WEDNESDAY INTO THURSDAY AS A COLD FRONT APPROACHES FROM THE WEST BRINGING WITH IT ANOTHER CHANCE OF RAIN SHOWERS LATER NEXT WEEK. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/... VFR CONDITIONS THROUGH SATURDAY. BRIEF PERIOD OF MVFR CIGS PSBL AT KMRB LATE TONIGHT. LIGHT AND VRB FLOW WILL INCREASE FROM THE S AFTR 13Z SAT. GUSTS MIXING IN BY MID MORNING...START TIME COULD BE +/- 1 HOUR THAN IN TAFS. BKN MID LVL CIGS SAT NIGHT-SUN NIGHT WITH PERIODIC MVFR CIGS PSBL WITH LIGHT PCPN. ANY PCPN SHOULD BE IN THE FORM OF RAIN. S-SW FLOW THROUGH THE PERIOD. SPOTTY SUB-VFR POSSIBLE MON EVE IN ISO SHWRS. SW FLOW AOB 10 KTS MON BECOMES NW AROUND 10-20 KTS GUSTING TO 25 KTS FOLLOWING FROPA MON EVE. VFR TUE W/ WIND TURNING N 10-20 KTS...THEN LIGHT AND VRB WIND TUE NIGHT INTO EARLY WED W/ SUB-VFR LIKELY IN LOW CIGS/LIGHT PRECIP. && .MARINE... NO MARINE HEADLINES EXPECTED THE REMAINDER OF TONIGHT AS HIGH PRESSURE BUILDS OVERHEAD...RESULTING IN LIGHT WINDS LESS THAN 10 KTS. HIGH PRESSURE WILL MOVE OFF TO THE EAST SATURDAY AND SOUTHERLY WINDS WILL INCREASE. A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR THE WATERS SATURDAY AFTERNOON. SWLY FLOW BECOMES MORE SLY SATURDAY NIGHT WITH SCA FOR UP TO 25 KT CHANNELING UP THE MAIN PORTION OF THE BAY AND 20 KT FOR EASTERN TRIBUTARIES AND LOWER TIDAL POTOMAC. 20 KT WINDS LIKELY CONTINUE INTO SUNDAY BEFORE THE PRESSURE GRADIENT SLACKENS. SOUTHWEST WIND BECOME NORTHWEST AND INCREASE TO 15-20 KTS W/ GUSTS TO 25 KTS MONDAY AS A COLD FRONT SINKS THROUGH THE WATERS. NORTHERLY CHANNELING COULD RESULT IN A CONTINUATION OF WIND GUSTS TO SMALL CRAFT ADVISORY LEVELS FOR A TIME TUESDAY OVER PARTS OF THE WATERS. WINDS BECOME LIGHT AND VARIABLE TUESDAY NIGHT INTO WEDNESDAY AS A WARM FRONT SLOWLY LIFTS ACROSS THE AREA. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM NOON SATURDAY TO 6 AM EST SUNDAY FOR ANZ530>534-537-539>541-543. SMALL CRAFT ADVISORY FROM NOON TO 6 PM EST SATURDAY FOR ANZ535- 536-538-542. && $$

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