462
FXUS62 KRAH 192038
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
340 PM EST WED FEB 19 2020
SYNOPSIS
A COLD FRONT WILL HOLD SOUTH OF THE AREA THROUGH TONIGHT, AS A LARGE
AREA OF ARCTIC HIGH PRESSURE BUILDS INTO THE REGION FROM THE
NORTHWEST. LOW PRESSURE WILL DEVELOP ALONG THE FRONT AND TRACK
EASTWARD OVER THE SOUTHEAST STATES THURSDAY THROUGH THURSDAY NIGHT.
HIGH PRESSURE WILL SETTLED OVER THE SOUTHEAST AND CAROLINAS FRIDAY
THROUGH SUNDAY.
NEAR TERM /THROUGH TONIGHT/
AS OF 340 PM WEDNESDAY...
PATCHY LIGHT RAIN HAS HELD ON OVER THE SE CWA, CORRESPONDING TO A
PASSING MID LEVEL SHEAR AXIS. INTERESTINGLY, WE'VE HAD MULTIPLE
REPORTS OF SLEET MIXING IN WITH RAIN WITHIN A NARROW SW-TO-NE BAND
OF PRECIP NOW EXTENDING THROUGH THE TRIANGLE, LIKELY A FUNCTION OF
THE DRYING JUST ALOFT AND SUBSEQUENT DROP IN THE WET BULB PROFILE,
ALLOWING A FEW ICE PELLETS TO SURVIVE THE TRIP TO THE GROUND DESPITE
SURFACE TEMPS THAT ARE WELL ABOVE NORMAL. NEVERTHELESS, AS THE
ARCTIC SURFACE HIGH BEGINS TO BUILD IN FROM THE NW (ALBEIT WITH THE
COLDEST AND MOST DENSE OF THIS AIR HOLDING WEST OF THE MOUNTAINS
INITIALLY), THE REMAINING PRECIP IS EXPECTED TO PUSH TO OUR SE THIS
EVENING, LEAVING PARTLY (N) TO MOSTLY (S) CLOUDY SKIES OVERNIGHT. WE
MAY SEE SOME LIGHT PRECIP (MOST LIKELY A MIX OF LIGHT RAIN AND
SLEET) SPREADING BACK INTO THE FAR SOUTHERN SECTIONS TOWARD MORNING
AS THE UPPER LEVEL WAVE AND SURFACE LOW APPROACH FROM THE W AND SW,
RESPECTIVELY, BRINGING IN RENEWED MOIST UPGLIDE AROUND 290K, BUT THE
VAST MAJORITY OF CENTRAL NC WILL REMAIN DRY THIS EVENING THROUGH
TONIGHT. EXPECT LOWS IN THE MID 30S TO AROUND 40. -GIH
SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/
AS OF 200 PM WEDNESDAY...
...WINTER WEATHER ADVISORY IN EFFECT FROM 10 AM THURSDAY TO 7 AM
FRIDAY...
CHANGES: STILL A GOOD BIT OF UNCERTAINTY WITH RESPECT TO AMOUNTS,
THOUGH THERE WILL LIKELY BE A "SWEET SPOT" AND A TIGHT GRADIENT
SOMEWHERE ACROSS CENTRAL NC. PRIMARY CHANGES FOR THIS FORECAST
ISSUANCE INCLUDE AN EARLIER START TIME FOR SNOW, PARTICULARLY ACROSS
THE NORTHERN HALF OF THE AREA AND AN UPTICK IN AMOUNTS ALONG THE I-
85/US-64 CORRIDORS. WHILE THE OVERALL WEATHER PATTERN REMAINS
SIMILAR TO PREVIOUS MODEL RUNS, CHANGES TO THE TEMPERATURE PROFILE
ALOFT HAVE RESULTED IN A BIT MORE P-TYPE UNCERTAINTY. THERE WILL
LIKELY BE A STRIPE OF WINTRY MIX ACROSS THE AREA AS THE RAIN MIXES
AND TRANSITIONS TO SNOW ACROSS THE AREA.
OVERALL PATTERN: A COLD FRONT WILL SETTLE SOUTH OF THE AREA, LAYING
ACROSS SC/GA THURSDAY MORNING WITH COOL HIGH PRESSURE RIDGING
SOUTHWARD AND ADVECTING COLD AIR INTO CENTRAL NC. WHILE THE SURFACE
FRONT WILL REMAIN SOUTH OF THE NC/SC BORDER, ALBEIT PIVOTING SOME TO
MORE SW/NE ORIENTATION, THE H85 FRONT WILL STALL OVER NC. AS A S/W
ALOFT RIDES ALONG THE H85 FRONT FROM THE MS VALLEY TOWARD THE MID-
ATLANTIC DURING THE DAY, A SURFACE LOW WILL DEVELOP OVER THE GULF
COAST/SOUTHEAST US IN RESPONSE. WITH ABUNDANT MOISTURE ADVECTION
ALOFT AND AND STRONG CYCLOGENESIS AT THE SURFACE OFF THE CAROLINA
COAST THERE WILL LIKELY BE AN AREA OF STRONG FRONTOGENESIS OVER NC
DURING THE AFT/EVE. THE COASTAL LOW WILL LIFT NORTHEAST ALONG THE NC
COAST THEN EASTWARD OUT OVER THE ATLANTIC THROUGH THURSDAY
EVE/NIGHT. MEANWHILE, THE PARENT UPPER TROUGH WILL SWING EASTWARD
THROUGH THE OH/TN VALLEY TOWARD THE MID-ATLANTIC/NE THURSDAY NIGHT.
PRECIPITATION WILL QUICKLY TAPER OFF AS THE UPPER TROUGH SWINGS
THROUGH THE AREA, EXITING THE REGION EARLY FRIDAY.
PRECIPITATION: RAIN WILL MOVE INTO THE AREA FROM THE SOUTH-SOUTHWEST
EARLY THURSDAY. WITH THE COOL, DRY AIR IN PLACE THIS RAIN WILL HELP
LOWER TEMPERATURES TO THE WET BULB TEMPERATURE (WHICH SHOULD BE IN
THE 29-32 DEGREE RANGE), ESPECIALLY ACROSS THE NORTHERN HALF OF THE
AREA. THE TRICKY PART OF THE PRECIPITATION WILL BE DETERMINING THE P-
TYPE AND TRANSITION TIMES. THERE IS A BIG POTENTIAL FOR ERROR IN
THIS REGARD, BUT THE MOST LIKELY SCENARIO WILL BE A QUICKER
TRANSITION TO SNOW ACROSS THE NORTH WITH LOWER LIQUID EQUIVALENT
PRECIPITATION TOTALS THAN ACROSS THE SOUTH. IN BETWEEN THERE WILL BE
HIGHER CHANCES OF MIXED PRECIPITATION WHICH COULD LOWER THE OVERALL
SNOW ACCUMULATION BUT POTENTIALLY CAUSE MORE ISSUES TRAVEL-WISE.
BASED ON THE MODEL SIMULATIONS FROM THIS MORNING, THERE SHOULD BE A
PERIOD OF ALL SNOW, MORE BRIEF IN SOME AREAS THAN OTHERS, ACROSS
CENTRAL NC BETWEEN THURSDAY MORNING AND DAYBREAK FRIDAY. WHILE
GENERALLY 0.5" TO 3" ARE MOST LIKELY ACROSS CENTRAL NC, THE MORE
REALISTIC SCENARIO WILL BE A VERY LOCALIZED AREA OF HIGHER AMOUNTS
AND A TIGHT GRADIENT FROM THAT TO TRACE AMOUNTS. OF COURSE, THE
THERMAL PROFILE AND SNOW-LIQUID RATIOS WILL BOTH IMPACT THE OVERALL
SNOW TOTALS WHEN IT'S ALL SAID AND DONE. AS PER USUAL, THE MOST
SIGNIFICANT ACCUMULATIONS WILL OCCUR ON ELEVATED/GRASSY SURFACES.
TEMPERATURES: HIGHS ON THURSDAY WILL OCCUR IN THE MORNING, TOPPING
OUT IN THE UPPER 30S NORTH TO MID 40S SOUTH. TEMPERATURES WILL LOWER
WITH THE ONSET OF RAINFALL, MORE QUICKLY ACROSS THE NORTH WITH
TEMPERATURES IN THE MID 30S ACROSS THE AREA EXPECTED BY SUNSET.
OVERNIGHT LOWS WILL DEPEND ON HOW QUICKLY THE LOW MOVES AWAY AND THE
PRECIP ENDS, BUT GENERALLY EXPECT A STEADY DECREASE TO AROUND
FREEZING UNTIL THE RAIN ENDS, WITH MORE RAPID COOLING IN ITS WAKE.
FOR NOW, EXPECT TEMPERATURES COULD BE IN THE MID 20S NW TO UPPER 20S
SE BY DAYBREAK FRIDAY.
WINDS: WINDS SHOULD BE NORTHEASTERLY THROUGHOUT THE PERIOD. WHILE
SUSTAINED WINDS WILL REMAIN IN THE 5-10 KT RANGE IN THE NW, GUSTING
TO 10-15 KTS IN THE EVE/NIGHT, WINDS ACROSS THE SOUTHEAST (IN CLOSER
PROXIMITY TO THE COASTAL LOW) WILL BE QUITE A BIT STRONGER AND
GUSTIER. EXPECT SUSTAINED WINDS ACROSS THE SANDHILLS AND COASTAL
PLAIN AROUND 15 KTS WITH GUSTS INTO THE MID 20S KTS.
FRIDAY AND FRIDAY NIGHT: THE PRECIPITATION SHOULD QUICKLY EXIT THE
AREA EARLY FRIDAY, WITH COOL, DRY WEATHER EXPECTED IN ITS WAKE.
WINDS WILL CONTINUE TO BE A BIT BREEZY/GUSTY, STRONGEST IN THE EAST
AND SOUTHEAST DURING THE DAY AND TAPERING OFF OVERNIGHT. SKIES
SHOULD RAPIDLY CLEAR DURING THE DAY, BUT WITH THE WINDS HIGHS MAY
REACH LOW 40S WEST WHILE TOPPING OUT IN THE UPPER 30S EAST.
OVERNIGHT, CLEAR SKIES AND LIGHT WINDS WILL RESULT IN GOOD
RADIATIONAL COOLING CONDITIONS WITH LOWS IN THE MID 20S EXPECTED.
LONG TERM /SATURDAY THROUGH WEDNESDAY/
AS OF 300 PM WEDNESDAY...
THE MID LEVEL SHORTWAVE TROUGH WILL BE PUSHING WELL OUT OVER THE
ATLANTIC SAT MORNING, LEAVING BROAD RIDGING ALOFT AND AN EXPANSIVE
SURFACE HIGH IN ITS WAKE. WE MAY SEE SOME OROGRAPHICALLY ENHANCED
HIGH CLOUDS MAINLY SAT AND SUN MORNING/EARLY AFTERNOON, BUT
OTHERWISE SKIES SHOULD BE MOSTLY CLEAR THROUGH MUCH OF THE WEEKEND,
WITH TEMPS RUNNING A BIT BELOW SEASONAL NORMALS, PEAKING IN THE LOW-
MID 50S SAT AND MID 50S TO NEAR 60 SUN.
THE PATTERN LOOKS TO TREND MILD BUT A BIT UNSETTLED MON-WED, WITH A
MEAN LONGWAVE TROUGH DEVELOPING TO OUR W. A PACIFIC-SOURCE LOW WILL
CROSS CA AND THE DESERT SOUTHWEST BEFORE BECOMING AN OPEN WAVE AND
CROSSING THE SOUTHERN PLAINS THROUGH SUN. THIS WILL DRAW THE SURFACE
FRONTAL ZONE BACK NORTHWARD INTO THE AREA WITH A SURFACE LOW
APPROACHING FROM THE WEST, SO EXPECT INCREASING CLOUDS SUN
EVENING/NIGHT FOLLOWED BY OVERCAST SKIES AND RAIN CHANCES FOR SUN
NIGHT THROUGH EARLY TUE AS THIS DAMPENING TROUGH AND SURFACE FRONTAL
SYSTEM PASS THROUGH. WE MAY GET INTO A BRIEF RESPITE LATE TUE INTO
EARLY WED, BUT A POLAR STREAM WAVE DIVING INTO THE CENTRAL/EASTERN
STATES MAY BRING IN ADDITIONAL RAIN CHANCES LATE WED. TEMPS WILL
GENERALLY PEAK IN THE MID 50S TO MID 60S, WITH LOWS HOLDING ABOVE
THE FREEZING MARK. -GIH
AVIATION /18Z WEDNESDAY THROUGH MONDAY/
AS OF 1155 AM WEDNESDAY...
A COLD FRONT HAS SETTLED JUST SE OF CENTRAL NC, BUT CLOUDS LINGERING
BEHIND (TO THE NORTH OF) THE FRONT KEPT SUB-VFR CONDITIONS OVER
RDU/FAY THROUGH LUNCHTIME, WITH 800-1500 FT AGL CIGS AND PATCHY RAIN
AND DRIZZLE. AT INT/GSO AND AT RWI, WHERE DRIER LOW-LEVEL AIR PUSHED
IN FROM THE N AND NE, RESPECTIVELY, CIGS BECAME VFR. AS THE DRIER
LOW LEVEL AIR CONTINUES ITS SOUTHWARD PUSH, CIGS WILL RISE TO VFR AT
RDU/FAY IN THE NEXT COUPLE OF HOURS. VFR CONDITIONS WILL THEN
DOMINATE AT ALL CENTRAL NC TERMINALS THROUGH SUNRISE, AS COOL HIGH
PRESSURE BUILDS INTO THE AREA FROM THE NW AND N. BUT CONDITIONS WILL
DETERIORATE STARTING AS EARLY AS MID MORNING THU, AS THE FRONT TO
OUR SOUTH HEADS BACK NORTH INTO NC, WITH A STRENGTHENING SURFACE LOW
TRACKING EASTWARD ALONG THE FRONT. PRECIPITATION WILL BE SPREADING
IN FROM THE SW IN THE MORNING, MOST LIKELY AS LIGHT RAIN MIXED WITH
A LITTLE SLEET, BUT INT/GSO MAY CHANGE TO MOSTLY SNOW TOWARD THE END
OF THE TAF VALID PERIOD (AFTER 16Z). CONDITIONS ARE EXPECTED TO
DETERIORATE TO IFR AT INT/GSO NEAR 16Z AND AT RDU/FAY NEAR 17Z, WITH
MVFR CONDITIONS POSSIBLE AFTER 17Z AT RWI.
LOOKING BEYOND 18Z THU, ADVERSE AVIATION CONDITIONS (MAINLY IFR) ARE
LIKELY THROUGH THE REST OF THU AND THU NIGHT AT ALL SITES, WITH
SEVERAL HOURS OF WINTRY PRECIPITATION OR A MIXTURE POSSIBLE. VFR
CONDITIONS ARE EXPECTED TO RETURN BEHIND THIS STORM SYSTEM STARTING
FRI MORNING, ALTHOUGH LINGERING WINTRY ACCUMULATION COULD BE
PROBLEMATIC ON PAVEMENT THROUGH FRI NIGHT. THESE VFR CONDITIONS ARE
LIKELY TO LAST THROUGH SUN BENEATH HIGH PRESSURE. THE NEXT STORM
SYSTEM WILL ARRIVE MON, BRINGING A GOOD CHANCE OF SUB-VFR CONDITIONS
WITH RAIN. -GIH
RAH WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY FROM 10 AM THURSDAY TO 7 AM EST FRIDAY
FOR NCZ007>011-021>028-038>043-073>078.
SYNOPSIS...HARTFIELD
NEAR TERM...HARTFIELD
SHORT TERM...KC
LONG TERM...HARTFIELD
AVIATION...HARTFIELD
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page