970  
FXUS61 KLWX 272008  
AFDLWX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC  
308 PM EST THU FEB 27 2020  
   
SYNOPSIS
 
 
LOW PRESSURE WILL SWIRL OVER SOUTHEASTERN CANADA THROUGH THE  
WEEKEND AS HIGH PRESSURE BUILDS IN FROM THE MIDWEST. THE HIGH  
WILL MOVE OFFSHORE AS A SLOW-MOVING FRONTAL SYSTEM FOLLOWS IN  
ITS WAKE EARLY NEXT WEEK.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
WINDS REMAIN GUSTY AS OF MID AFTERNOON, BUT PEAK GUSTS HAVE  
COME DOWN IN MAGNITUDE SOMEWHAT AS THE BEST PRESSURE GRADIENT  
RETREATS TO THE NORTHEAST. ANOTHER DISTURBANCE JUST UPSTREAM  
OVER EASTERN OHIO INTO NORTHERN WEST VIRGINIA WILL PUSH EASTWARD  
BY DARK, BRINGING ANOTHER SURGE OF WIND WITH IT OVER THE HIGHER  
TERRAIN. AT THIS TIME, HOWEVER, INCREASING SATURATION IN THE  
LOW LEVELS AND LOSS OF BETTER DIURNAL MIXING SHOULD PRECLUDE  
MORE FREQUENT GUSTS OF 45 MPH OR GREATER. THEREFORE, NO WIND  
ADVISORIES HAVE BEEN ISSUED AT THIS TIME.  
 
BRISK CONDITIONS WILL CONTINUE TONIGHT WITH BREEZY NORTHWESTERLY  
WINDS (GUSTY IN THE EVENING, THEN GRADUALLY DIMINISHING OVERNIGHT).  
A FEW FLURRIES OR A SNOW SHOWER ARE POSSIBLE, PARTICULARLY OVER  
NORTHERN MARYLAND, WITH MORE FREQUENT SNOW SHOWERS LIKELY ALONG  
AND WEST OF THE ALLEGHENY FRONT AS AN AREA OF DEEPER SATURATION  
AND LIFT CROSSES. MORE WESTERLY FLOW WILL CAUSE MUCH OF THE  
BEST MOISTURE TO BE BLOCKED BY UPSTREAM RIDGES EXCEPT PERHAPS  
WESTERN GRANT COUNTY INTO WESTERN MINERAL COUNTY, WHERE THE BEST  
CHANCE IS FOR LOW-END ADVISORY CRITERIA TONIGHT (THOUGH  
CONFIDENCE IS CURRENTLY TOO LOW FOR AN ADVISORY AT THE MOMENT).  
 
LOWS WILL BE IN THE 20S FOR MOST OF THE AREA, EXCEPT NEAR  
FREEZING IN THE IMMEDIATE LARGER URBAN CENTERS AND NEAR THE  
CHESAPEAKE BAY. WIND CHILLS AROUND 0 ARE POSSIBLE OVER THE  
HIGHER ELEVATIONS, BUT THIS IS ABOUT 10 DEGREES WARMER THAN ANY  
HEADLINE CRITERIA FOR THOSE AREAS.  
 

 
   
SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/
 
 
NORTHWEST FLOW IS ANTICIPATED FRIDAY THROUGH SATURDAY. A  
SECONDARY/REINFORCING COLD FRONT AND ATTENDANT UPPER SHORTWAVE  
WILL CROSS FRIDAY. MODELS INDICATE THE POTENTIAL FOR DEEP  
MIXING. I DON'T THINK THIS DEEP MIXING (UP TO 9000 FEET IN THE  
NAM) COMES TO FRUITION IN A PREVAILING SENSE. RATHER, MEAN LAYER  
MIXING (RESULTING IN SURFACE WIND GUSTS UP TO 30 MPH) SEEMS  
MORE LIKELY. THERE IS A POTENTIAL FOR ISOLATED RAIN/SNOW  
SHOWERS, THOUGH, AND ANY SHOWER COULD RESULT IN SOME ADDED  
DOWNWARD MOMENTUM TRANSFER THROUGH EVAPORATIVE COOLING PROCESSES  
(AIR ACCELERATES WHEN PRECIPITATION DRIES UP BEFORE REACHING  
THE GROUND), RESULTING IN ISOLATED GUSTS IN EXCESS OF 40 MPH.  
NEAR- SURFACE TEMPERATURES SHOULD BE WARM ENOUGH TO PRECLUDE ANY  
APPRECIABLE SNOWFALL ACCUMULATION EAST OF THE MOUNTAINS, SO  
ALTHOUGH FLAKES MAY FLY, THEY PROBABLY WON'T STICK.  
 
COLD/DRY ADVECTION SHOULD LEAD TO A DRIER BUT COLDER SATURDAY  
WITH CONTINUED BREEZY CONDITIONS (ALBEIT A BIT LIGHTER).  
 

 
   
LONG TERM /SUNDAY THROUGH THURSDAY/
 
 
A LARGE TROUGH AT MID-UPPER LEVELS WILL MOVE OFFSHORE ON SUNDAY,  
ALLOWING HIGH PRESSURE TO BUILD IN AT THE SURFACE OVER THE  
SOUTHEASTERN U.S. MOSTLY SUNNY SKIES ARE EXPECTED AS THE HIGH  
SETTLES TO OUR SOUTH, WITH LIGHT WINDS OUT OF THE WEST. HIGH  
TEMPERATURES ON SUNDAY WILL BE IN THE LOWER 50S ACROSS MUCH OF  
THE AREA.  
 
THE PATTERN WILL TURN MUCH MORE ACTIVE HEADING INTO EARLY-MIDDLE  
PORTIONS OF NEXT WEEK. THE SUBTROPICAL JET FEEDING INTO THE  
SOUTHWESTERN U.S. WILL STRENGTHEN OVER THE COMING DAYS IN  
RESPONSE TO OUTFLOW FROM AN AREA OF ACTIVE CONVECTION IN THE  
SOUTHEASTERN PACIFIC OCEAN. MEANWHILE, A STRONG RIDGE-BUILDING  
EVENT IN THE NORTHEASTERN PACIFIC OCEAN WILL DEPOSIT A  
POSITIVELY TILTED TROUGH EQUATORWARD TOWARD THE SOUTHWESTERN  
U.S., HELPING TO FURTHER STRENGTHEN THE SUBTROPICAL JET. IN THE  
NORTHERN STREAM, MULTIPLE SHORTWAVES WILL CONTINUE TO PROGRESS  
FROM WEST TO EAST NEAR THE U.S./CANADIAN BORDER. A LOW-LEVEL  
FRONTAL BOUNDARY WILL BE DRIVEN SOUTHWARD TOWARD OUR AREA IN  
RESPONSE TO A LEAD SHORTWAVE AND ASSOCIATED SURFACE LOW TRACKING  
ACROSS QUEBEC ON MONDAY. AS DEEP-LAYER SOUTHWESTERLY FLOW  
BECOMES ESTABLISHED ACROSS THE AREA LATE MONDAY INTO TUESDAY,  
MOISTURE TRANSPORT OUT OF THE GULF OF MEXICO WILL INCREASE.  
SHOWERS WILL BE POSSIBLE MONDAY AFTERNOON THROUGH TUESDAY AS  
MOISTURE INTERACTS WITH THE SLOWLY MOVING FRONTAL BOUNDARY.  
 
WITH MANY MOVING PARTS IN BOTH THE NORTHERN AND SOUTHERN STREAMS,  
FORECAST UNCERTAINTY INCREASES SUBSTANTIALLY MOVING TOWARD WEDNESDAY.  
THE AFOREMENTIONED TROUGH OVER THE DESERT SOUTHWEST WILL EJECT  
EASTWARD TOWARD THE CENTRAL U.S. TUESDAY NIGHT INTO WEDNESDAY,  
WHILE ANOTHER SHORTWAVE LOCATED WITHIN THE NORTHERN STREAM  
PROGRESSES ACROSS THE NORTH-CENTRAL U.S. HOW THESE TWO  
DISTURBANCES INTERACT WILL ULTIMATELY DETERMINE OUR SENSIBLE  
WEATHER ON WEDNESDAY. POSSIBILITIES RANGE ANYWHERE FROM COLD AND  
RAINY ON THE COOL SIDE OF THE SURFACE BOUNDARY, TO TEMPERATURES  
IN THE 70S IF THE PATTERN BECOMES MORE AMPLIFIED AND WE END UP  
IN THE SURFACE WARM SECTOR. WE WILL CONTINUE TO MONITOR TRENDS  
AND REFINE THE FORECAST AS WE MOVE CLOSER TO THE EVENT.  
 

 
   
AVIATION /20Z THURSDAY THROUGH TUESDAY/
 
 
GUSTY WESTERLY FLOW WILL CONTINUE INTO THIS EVENING WITH GUSTS  
GENERALLY IN THE 30 TO 35 KNOT RANGE. WINDS SHOULD BACK TO 250-270  
LATE THIS AFTERNOON AHEAD OF AN ATMOSPHERIC DISTURBANCE/WEAK  
SURFACE REFLECTION. OTHERWISE, VFR SCATTERED TO BROKEN CUMULUS  
AROUND 5000 FEET ARE EXPECTED. A FLURRY OR TWO MAY PASS NEAR  
MRB (LESS LIKELY BUT NOT IMPOSSIBLE NEAR BWI/IAD/MTN) THROUGH  
03Z AS THE DISTURBANCE CROSSES, BUT VISIBILITY RESTRICTIONS (IF  
ANY) SHOULD BE BRIEF.  
 
WINDS WILL GRADUALLY SUBSIDE TONIGHT, BUT GUSTS RESUME AFTER  
13-14Z FRIDAY. MODEL SOUNDINGS SHOW THE POTENTIAL FOR VERY DEEP  
MIXING BETWEEN 17Z-22Z FRIDAY, ALONG WITH INVERTED-V SIGNATURES  
BELOW THE CLOUD BEARING LAYER (WHICH BECOMES SATURATED BETWEEN  
5000 TO 10000 FEET DURING THIS TIME). AS SUCH, ANTICIPATE  
PREVAILING GUSTS GENERALLY AROUND 25 TO PERHAPS 30 KNOTS, BUT  
MUCH STRONGER GUSTS TO AROUND 40 KNOTS MAY BE POSSIBLE NEAR ANY  
RAIN OR SNOW SHOWER THAT DEVELOPS AHEAD OF ANOTHER MID LEVEL  
WAVE AND ASSOCIATED SURFACE TROUGH.  
 
VFR CONDITIONS ARE EXPECTED AT THE TERMINALS SUNDAY THROUGH MONDAY  
MORNING. SHOWERS APPEAR POSSIBLE BY MONDAY AFTERNOON.  
 

 
   
MARINE
 
 
WESTERLY FLOW GUSTING 20 TO 30 KNOTS IS EXPECTED THIS EVENING.  
WINDS SHOULD BECOME MORE NORTHWESTERLY BY DAYBREAK. GUSTS OVER  
MORE SHELTERED WATERS (MIDDLE/UPPER TIDAL POTOMAC) LIKELY  
DIMINISH FOR A TIME OVERNIGHT BEFORE REINVIGORATING DURING THE  
DAY FRIDAY. MODEL SOUNDINGS SHOW THE POTENTIAL FOR DEEP MIXING  
INTO A MUCH STRONGER WIND FIELD FRIDAY MIDDAY AND AFTERNOON,  
THOUGH PREVAILING WINDS SHOULD BE WITHIN THE SMALL CRAFT  
ADVISORY CRITERIA RANGE (18 TO 33 KNOTS). A FEW GUSTS TO GALE  
FORCE CAN'T BE RULED OUT, HOWEVER, PARTICULARLY NEAR ANY RAIN OR  
SNOW SHOWERS THAT DEVELOP AHEAD OF AN APPROACHING DISTURBANCE.  
 
WINDS ABATE OVER MORE SHELTERED WATERS AGAIN FRIDAY NIGHT BEFORE  
MIXING INCREASES AGAIN DURING THE DAY SATURDAY, STILL OUT OF  
THE NORTHWEST.  
 
SUB-SCA LEVEL WINDS ARE EXPECTED OVER THE WATERS BOTH SUNDAY AND  
MONDAY. WINDS WILL BE OUT OF THE WEST ON SUNDAY, AND OUT OF THE  
SOUTH/SOUTHWEST ON MONDAY.  
 

 
   
LWX WATCHES/WARNINGS/ADVISORIES
 
 
DC...NONE.  
MD...NONE.  
VA...NONE.  
WV...NONE.  
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EST SATURDAY FOR ANZ530>534-  
537-539>541-543.  
SMALL CRAFT ADVISORY UNTIL 6 PM EST FRIDAY FOR ANZ538-542.  
SMALL CRAFT ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR ANZ535-536.  
SMALL CRAFT ADVISORY FROM 9 AM TO 6 PM EST FRIDAY FOR ANZ535-  
536.  
 

 
 

 
SYNOPSIS...DHOF  
NEAR TERM...DHOF  
SHORT TERM...DHOF  
LONG TERM...ADS/KJP  
AVIATION...ADS/DHOF/KJP  
MARINE...ADS/DHOF/KJP  
 
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