446
FXUS62 KRAH 191958
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
258 PM EST TUE NOV 19 2019
SYNOPSIS
A SERIES OF STRONG UPPER LEVEL DISTURBANCES WILL CROSS THE REGION
THROUGH TONIGHT. HIGH PRESSURE WILL BUILD OVER THE AREA WEDNESDAY
AND THURSDAY. THIS HIGH PRESSURE AREA WILL THEN PUSH TO OUR SOUTH ON
FRIDAY, AS A COLD FRONT APPROACHES FROM THE NORTH.
NEAR TERM /THROUGH TONIGHT/
AS OF 155 PM TUESDAY...
THE MEAN MID LEVEL TROUGH SITTING OVER EASTERN NOAM FEATURES TWO
SUBTLE BUT DISTINCT WAVES IN CLOSE PROXIMITY: ONE NOW SHIFTING ENE
WITH A NEGATIVE TILT THROUGH THE CENTRAL CAROLINAS, AND THE SECOND
CLOSE ON ITS HEELS, DIVING SOUTHEASTWARD INTO THE S APPALACHIANS.
THIS MORNING'S LOW CLOUDS HAVE FINALLY LIFTED AND MIXED OUT OVER NW
AND FAR N SECTIONS, LESS SO OVER THE COASTAL PLAIN/SANDHILLS,
ALTHOUGH THESE TOO SHOULD START TO MIX OUT IN EARNEST AS THE LEAD
VORTICITY CENTER NOW MOVING OFF THE SC COAST PUSHES THE TROUGH AXIS
OFFSHORE. BUT CLOUDS WILL RETURN THIS EVENING AS THE SHEARED,
ELONGATED VORTICITY LOBE SWINGS SE THROUGH THE CAROLINAS, BRINGING
STRATOCU/ALTOCU MAINLY TO N SECTIONS OF CENTRAL NC, ACCOMPANIED BY
PASSAGE OF WEAK SURFACE LOW PRESSURE. WHILE A FEW SPRINKLES ARE
POSSIBLE GIVEN THIS POTENT LARGE SCALE LIFT, WIDESPREAD MEASURABLE
PRECIP APPEARS UNLIKELY BASED ON UPSTREAM AND MODEL-PROJECTED
MOISTURE PROFILES, SO WILL MAINTAIN SUB-15% POPS. THIS FORCING FOR
ASCENT WILL TRACK TO OUR EAST AND OFF THE COAST VERY LATE TONIGHT
INTO WED MORNING, AND AS SURFACE WINDS BECOME UNIFORM NORTHWESTERLY
AND STRENGTHEN, THE RESULTING DOWNSLOPE FLOW ALONG WITH DCVA AND
RISING HEIGHTS ALOFT WILL PROMPT A CLEARING TREND STARTING VERY LATE
TONIGHT. WITH THE DELAY IN LOWER DEWPOINTS AND CONTINUED LIGHT
SURFACE WINDS IN OUR SE SECTIONS, HOWEVER, THERE MAY STILL BE
PATCHES OF SHALLOW GROUND FOG THERE LATE TONIGHT. EXPECT LOWS IN THE
MID 30S TO AROUND 40. -GIH
SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/
AS OF 230 PM TUESDAY...
THE MEAN TROUGH AXIS WILL CONTINUE TO DEEPEN AS IT HEADS E OFF THE
MID ATLANTIC AND NORTHEAST COAST WED MORNING, LEAVING RISING HEIGHTS
AND DECELERATING NW MID LEVEL FLOW IN ITS WAKE OVER NC. APART FROM
SOME LINGERING EARLY-MORNING CLOUDS IN THE SE, SKIES SHOULD BE
GENERALLY CLEAR WED, WITH LITTLE MORE THAN SOME FLAT HIGH-BASED CU
AS THE COLUMN DRIES AND STABILIZES. SURFACE HIGH PRESSURE EXTENDING
FROM THE NORTH CENTRAL GULF UP ALONG THE SOUTHERN AND MID MISS
VALLEY THIS AFTERNOON WILL DRIFT NE OVER THE OHIO VALLEY AND INTO
THE INTERIOR MID ATLANTIC REGION THROUGH WED NIGHT, RESULTING IN A
PERSISTENT LOW LEVEL THERMAL TROUGH EXTENDING THROUGH CENTRAL NC
WITH THICKNESSES REMAINING SLIGHTLY BELOW NORMAL. BUT WITH AMPLE
SUNSHINE TO SOMEWHAT OFFSET THE CAA, TEMPS SHOULD STILL PEAK WITHIN
A COUPLE OF DEGREES OF NORMAL, IN THE UPPER 50S TO LOWER 60S. LOWS
WED NIGHT IN THE LOW-MID 30S WITH GOOD RADIATIONAL COOLING EXPECTED,
ALTHOUGH WE SHOULD SEE SOME HIGH THIN CLOUDINESS SPREADING IN LATE
AHEAD OF A DAMPENING WAVE (THE REMNANTS OF THE CLOSED LOW CURRENTLY
OFF BAJA) MOVING NE THROUGH THE MIDWEST. -GIH
LONG TERM /THURSDAY THROUGH TUESDAY/
AS OF 255 PM TUESDAY...
THROUGH THURSDAY: THE SURFACE HIGH WILL SHIFT SLOWLY SOUTHEASTWARD
THROUGH THURSDAY NIGHT WHILE THE RIDGE ALOFT DAMPENS OVER THE
REGION. CLOUDS WILL START TO CREEP IN FROM THE WEST THURSDAY NIGHT
AS THE NEXT COLD FRONT APPROACHES. WINDS BOTH ALOFT AND AT THE
SURFACE WILL BACK TO MORE WEST/SOUTHWESTERLY BY FRIDAY MORNING.
TEMPERATURES SHOULD BE NEAR TO SLIGHTLY BELOW NORMAL WITH HIGHS IN
THE MID 50S TO LOW 60S. AS A RESULT OF THE INCREASING CLOUDS AND
SOUTHWESTERLY FLOW THURSDAY NIGHT, LOWS WILL BE QUITE A BIT HIGHER
THAN THE PREVIOUS NIGHT, GENERALLY IN THE MID 40S.
FRIDAY THROUGH SUNDAY: VARIOUS INTERACTIONS BETWEEN NORTHERN AND
SOUTHERN STREAM FEATURES WILL SHAPE THE WEATHER FOR CENTRAL NC OVER
THE WEEKEND. THERE ARE SEVERAL FEATURES AT PLAY HERE. FIRST, THERE
IS A TROPICAL SYSTEM OVER THE PACIFIC THAT WILL MOVE NORTHEASTWARD
OVER THE BAJA AND INTO THE SOUTHWEST US TONIGHT. MEANWHILE, A
NORTHERN STREAM TROUGH OVER THE PACIFIC NORTHWEST WILL AMPLIFY AS A
S/W LOW SWINGS AROUND THE BASE OF THE TROUGH. THE S/W LOW WILL BREAK
OFF FROM THE PARENT TROUGH, CLOSING OFF OVER OR/CA/NV THIS EVENING.
THESE TWO UPPER LOWS WILL INTERACT AS THE NORTHERN STREAM LOW
ABSORBS SOME OF THE ENERGY FROM THE TROPICAL SYSTEM, DEEPENING
ITSELF IN THE PROCESS OVER THE SOUTHWEST US TONIGHT/EARLY WED. AS
THE NORTHERN STREAM LOW BECOMES DOMINANT AND NEARLY STATIONARY OVER
THE INTERMOUNTAIN WEST, THE REMNANTS OF THE TROPICAL/SOUTHERN STREAM
LOW WILL LIFT EAST-NORTHEAST AS A SHORTWAVE. A SURFACE LOW WILL
DEVELOP IN RESPONSE TO THE S/W ALOFT WITH FRONTOGENESIS OVER THE
PLAINS/MIDWEST WED NIGHT/THU. THE FRONT WILL PROGRESS EASTWARD
THROUGH THE MIDWEST AS THE SURFACE LOW LIFTS/MOVES EAST-NORTHEAST
TOWARD AND THROUGH THE GREAT LAKES. THE EASTWARD PROGRESSION OF THE
FRONT WILL SLOW/STALL AS THE BEST ENERGY LIFTS FURTHER AWAY FROM THE
AREA AND HIGH PRESSURE LINGERS OVER THE SOUTHEAST US. THE COLD
CANADIAN HIGH WILL SETTLE SOUTH OVER THE NORTHERN PLAINS/WESTERN
GREAT LAKES THURSDAY NIGHT. IT STILL APPEARS THE NORTHERN STREAM
TROUGH WILL REMAIN ANCHORED WITH THE CLOSED LOW OVER THE IM WEST
UNTIL IT MOVES EASTWARD OVER THE ROCKIES THU NIGHT. AS THE LOW WILL
SHIFTS EASTWARD OVER INTO THE PLAINS/MIDWEST FRIDAY THE NORTHERN
STREAM TROUGH WILL DETACH FROM IT AND SWING THROUGH THE GREAT LAKES
AND INTO NEW ENGLAND. SUBSEQUENTLY, THE LOW WILL OPEN INTO A TROUGH
OVER THE MIDWEST, ONCE AGAIN STRENGTHENING FRONTOGENESIS, WITH A
SURFACE LOW DEVELOPING ALONG THE FRONT IN THE VICINITY OF LA/MS/THE
SOUTHERN APPALACHIANS FRIDAY NIGHT. ALTHOUGH THERE ARE STILL SOME
SUBTLE DIFFERENCES BETWEEN THE MEDIUM-RANGE MODELS WITH THE
PROGRESSION OF THE SURFACE LOW AND COLD FRONT, THEY ARE IN
SURPRISINGLY GOOD AGREEMENT. THE AFOREMENTIONED SURFACE LOW IS
EXPECTED TO TREK NORTHEAST ALONG THE SPINE OF THE MTNS AS A
SECONDARY LOW DEVELOPS OVER THE CAROLINAS, ENHANCING LIFT AND THUS
PRECIPITATION CHANCES/AMOUNTS OVER THE AREA. BEST CHANCES FOR RAIN
WILL BE BETWEEN MIDNIGHT SATURDAY AND MIDNIGHT SUNDAY. THE FRONT AND
ASSOCIATED RAINFALL SHOULD EXIT THE AREA SUNDAY, WITH A RETURN TO
DRY WEATHER. FRIDAY WILL LIKELY BE THE WARMEST DAY OF THE PERIOD,
ALBEIT CLOUDY. WEEKEND TEMPERATURES WILL BE HIGHLY DEPENDENT ON THE
FRONT AND ASSOCIATED RAINFALL.
MONDAY AND TUESDAY: PRIMARILY DRY WEATHER EXPECTED THROUGH TUESDAY
AS SURFACE HIGH PRESSURE BUILDS INTO THE REGION IN THE WAKE OF THE
FRONT. ANOTHER FRONTAL SYSTEM WILL DEVELOP OVER THE PLAINS AND
PROGRESS EASTWARD THROUGH MID-WEEK.
AVIATION /18Z TUESDAY THROUGH SUNDAY/
AS OF 123P PM TUESDAY...
IFR TO MVFR CONDITIONS HELD ON FOR MUCH OF THE MORNING BUT HAVE
BEGUN TO BREAK UP IN THE LAST FEW HOURS AS DRIER AIR ALOFT HAS
STARTED TO MIX GROUNDWARD WITH DECREASING SURFACE-BASED STABILITY.
INT/GSO HAVE ALREADY BECOME SCATTERED WITH THEIR LOW CLOUDS, AND THE
BROKEN IFR/MVFR CIGS AT RDU/RWI/FAY SHOULD CONTINUE TO SLOWLY LIFT
WITH PERIODIC BREAKS THROUGH 22Z. AFTER THIS TIME, SCATTERED TO
BROKEN STRATOCU (VFR) TOPPED WITH MID CLOUDS WILL SPREAD IN FROM THE
NW AS MID LEVEL ENERGY DIVES INTO THE TROUGH BASE AND OVER NC THIS
EVENING INTO THE OVERNIGHT HOURS. THERE IS A CHANCE FOR SHALLOW
GROUND FOG LATE TONIGHT AT RDU/FAY/RWI WITH LINGERING NEAR-SURFACE
MOISTURE, BUT UNCERTAINTY IS HIGH AND COVERAGE SHOULD BE LOW.
OTHERWISE, CLEARING IS EXPECTED FROM THE W TOWARD DAYBREAK WED, AS
THE TROUGH AXIS SHIFTS TO OUR E WITH RISING HEIGHTS ALOFT AND LOW
LEVEL DRYING AS A STEADY DOWNSLOPE NW FLOW DEVELOPS. VFR CONDITIONS
ARE LIKELY FROM MID MORNING ON.
LOOKING BEYOND 18Z WED, VFR CONDITIONS ARE EXPECTED TO HOLD THROUGH
AT LEAST THE FIRST PART OF FRI AS HIGH PRESSURE BUILDS OVER THE
AREA, ALTHOUGH THERE IS A RISK FOR LLWS EARLY FRI MORNING. AN
APPROACHING UPPER TROUGH AND SURFACE LOW WILL BRING INCREASING
CHANCES FOR SUB-VFR CONDITIONS AND RAIN STARTING LATE FRI AND
CONTINUING THROUGH SAT NIGHT, WITH STRONG/GUSTY/SHIFTING WINDS. VFR
CONDITIONS ARE EXPECTED SUN AS HIGH PRESSURE RETURNS. -GIH
RAH WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...HARTFIELD
NEAR TERM...HARTFIELD
SHORT TERM...HARTFIELD
LONG TERM...KC
AVIATION...HARTFIELD
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