844
FXUS62 KRAH 190302
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1000 PM EST TUE DEC 18 2018
SYNOPSIS
HIGH PRESSURE WILL TRANSVERSE THE REGION TONIGHT AND INCH OFFSHORE
ON WEDNESDAY. A DEVELOPING STORM SYSTEM WILL MOVE SLOWLY EAST THROUGH
THE CENTRAL AND EASTERN UNITED STATES THURSDAY THROUGH FRIDAY NIGHT,
BRINGING UNSETTLED CONDITIONS TO OUR AREA. THIS STORM SYSTEM WILL
MOVE OFF THE EAST COAST EARLY SATURDAY, THEN HIGH PRESSURE WILL
BUILD OVER THE REGION SATURDAY THROUGH SUNDAY.
NEAR TERM /TODAY THROUGH TONIGHT/
AS OF 1000 PM TUESDAY...
LATEST SFC ANALYSIS SHOWS THE EASTERN PERIPHERY OF THE SFC HIGH NOW
INCHING EAST OF THE APPALACHIANS, EDGING SOUTHWARD INTO THE MID
ATLANTIC STATES. THIS HAS ALLOWED SKIES TO REMAIN RELATIVELY CLEAR
WITH THE EXCEPTION OF SOME THIN AND WISPY UPPER-LEVEL CIRRUS CLOUDS
SPURRED ON BY A DECAYING SHORTWAVE EJECTING OUT OF THE SOUTHERN
STREAM JET. THE SFC HIGH PRESSURE IS EXPECTED TO CONTINUE TO BUILD
ACROSS THE AREA THROUGH TONIGHT, ALLOWING IDEAL RADIATIONAL COOLING
CONDITIONS TO PREVAIL. THIS SHOULD RESULT IN OVERNIGHT LOW TEMPS
DIPPING TO NEAR FREEZING, WITH SOME UPPER-20S NOT OUT OF THE
QUESTION IN THE NORMAL COLD SPOTS ACROSS THE NORTHERN AND WESTERN
PIEDMONT OF THE STATE.
SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/
AS OF 320 PM TUESDAY...
DURING THIS PERIOD WE'LL BEGIN TO SEE THE INFLUENCE OF A
STRENGTHENING MID LEVEL TROUGH TRAVERSING THE CENTRAL CONUS. THE
SOUTHERN STREAM LOW, NOW DEEPENING OVER THE TX PANHANDLE, WILL CROSS
TX/LA THROUGH WED NIGHT, AND THE INJECTION OF ENERGY FROM THE FASTER
NORTHERN STREAM WILL RESULT IN A DEEP, FULL-LATITUDE TROUGH, LOCATED
JUST W OF THE MISS VALLEY BY DAYBREAK THU. HIGH PRESSURE SITUATED
OVER NC EARLY WEDNESDAY WILL SHIFT OFFSHORE WEDNESDAY NIGHT,
INDUCING A MOIST LOW LEVEL FLOW FROM THE E AND SE ALONG WITH COASTAL
INVERTED TROUGH FORMATION. ALL OF THIS WILL RESULT IN INCREASING
CLOUDINESS FROM THE S OVER CENTRAL NC WED AFTERNOON INTO WED NIGHT,
ALONG WITH A RISK OF A FEW SPRINKLES OR SHOWERS OVER SE THEN E
SECTIONS OVERNIGHT INTO THU MORNING AS MOIST ISENTROPIC UPGLIDE
STRENGTHENS AND DEEPENS THROUGH THE 285K-295K DEPTH. EXPECT A TREND
TO OVERCAST SKIES LATE WED EVENING, WITH ONLY MINOR IMPACTS TO
TEMPERATURES EXPECTED. HIGHS SHOULD BE 51 (NORTH) TO 58 (SOUTH) WITH
NEAR TO SLIGHTLY ABOVE NORMAL THICKNESSES. THE INCREASE IN CLOUDS
WILL KEEP TEMPS UP WED NIGHT, YIELDING LOWS OF 38 (NORTH) TO 47
(SOUTH).
LONG TERM /THURSDAY THROUGH TUESDAY/
AS OF 240 PM TUESDAY...
FORECAST REMAINS ON TRACK REGARDING THE RAINFALL EVENT MOVING INTO
AND THROUGH THE CAROLINAS THURSDAY AND FRIDAY.
THURSDAY AND FRIDAY: A HIGHLY AMPLIFIED UPPER LEVEL TROUGH OVER THE
MIDWEST WILL PROGRESS EASTWARD THROUGH FRIDAY, WITH STRONG SOUTHERLY
FLOW AHEAD OF THE SYSTEM ADVECTING WARM, MOIST AIR INTO THE GULF
COAST AND SOUTHEAST US. THE SURFACE PATTERN APPEARS SIMILAR TO THE
LAST EVENT, WHERE THE PRIMARY LOW REMAINS OVER THE SOUTHERN
APPALACHIANS WHILE TWO SECONDARY LOWS SWING THROUGH THE CAROLINAS.
THE SURFACE LOWS ALL MERGE TOGETHER OVER THE MID-ATLANTIC AND
NORTHEAST US ON FRIDAY BEFORE LIFTING AWAY FROM THE AREA. AS WITH
THE LAST EVENT, EXPECT RAIN TO MOVE IN FROM THE SOUTH, HEAVIEST
THURSDAY EVENING THROUGH FRIDAY MORNING. SOME WRAP AROUND SHOWERS
ARE LIKELY ON FRIDAY AS THE UPPER LEVEL WAVE SWINGS THROUGH THE
CAROLINAS AND VIRGINIAS. FOR NOW, TIMING AND TRACK ARE NOT CERTAIN
ENOUGH TO PUT ANY THUNDER IN THE FORECAST JUST YET. RAINFALL
AMOUNTS WILL PROBABLY BE IN THE 1 TO 2 INCH RANGE, WITH HIGHER
AMOUNTS FARTHER EAST. TEMPERATURES WILL BE QUITE MILD, WITH HIGHS IN
THE LOW 50S NW TO MID 60S SE THURSDAY AND FRIDAY AND LOWS THURSDAY
NIGHT INT HE MID 40S NW TO MID 50S SE. DEPENDING ON THE TIMING OF
THE SYSTEM EXITING THE AREA, THE FRONTAL PASSAGE AND ADVECTION OF
COOLER AIR FROM THE NW, LOWS FRIDAY NIGHT ARE MORE UNCERTAIN. FOR
NOW EXPECT LOWS IN THE MID 30S NW TO LOW 40S SE.
SATURDAY THROUGH TUESDAY: HIGH PRESSURE WILL BUILD INTO THE
CAROLINAS IN THE WAKE OF THE EXITING SYSTEM/FRONT. EXPECT THIS PART
OF THE FORECAST TO BE DRY AND SEASONABLE WITH NEAR NORMAL
TEMPERATURES AND GENERALLY CLEAR SKIES.
AVIATION /23Z TUESDAY THROUGH SATURDAY/
AS OF 640 PM TUESDAY...
VFR CONDITIONS ARE EXPECTED TO PERSIST ACROSS CENTRAL NC FOR AT
LEAST THE NEXT 24 HOURS AS HIGH PRESSURE REMAINS DOMINANT. CLOUDS
ARE EXPECTED TO OVERSPREAD THE REGION ON WEDNESDAY AFTERNOON AND
EVENING, AND BEGIN TO LOWER. THEY SHOULD, HOWEVER, REMAIN VFR
THROUGH 00Z THURSDAY. WINDS WILL REMAIN LIGHT AND VARIABLE
OVERNIGHT, WITH A LIGHT SOUTHEASTERLY FLOW ESTABLISHING WEDNESDAY
AFTERNOON BEFORE DIMINISHING AGAIN IN THE EVENING.
LOOKING BEYOND 00Z THU: SUB-VFR CONDITIONS ARE LIKELY TO FORM AFTER
MIDNIGHT THURSDAY MORNING AND PERSIST THROUGH THE END OF THE WORK-
WEEK AS BOUNDARY LAYER MOISTURE INCREASES. THIS WILL LIKELY LEAD TO
LOWERING CIGS/VSBYS, WHICH MAY AT TIMES DROP TO IFR/LIFR RANGES
WHILE HEAVY RAIN SHOWERS PASS OVER THE FORECAST AREA. IMPROVEMENT IS
EXPECTED FRI NIGHT WITH VFR CONDITIONS LIKELY AGAIN BY SAT AFTERNOON
AS THE STORM SYSTEM MOVES OFF THE COAST AND HIGH PRESSURE BUILDS
INTO THE AREA.
RAH WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...JJM/HARTFIELD
NEAR TERM...JJM
SHORT TERM...JJM/HARTFIELD
LONG TERM...KC
AVIATION...JJM
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