003
FXUS62 KRAH 091150
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
650 AM EST TUE FEB 9 2010
SYNOPSIS
A LOW PRESSURE SYSTEM WILL APPROACH FROM THE SOUTHWEST TODAY...AND
WILL MOVE NORTHEAST MOVING OFF THE NORTH CAROLINA COAST TONIGHT.
STRONG WINDS BEHIND A COLD FRONTAL PASSAGE WEDNESDAY MORNING WILL
AFFECT THE AREA ON WEDNESDAY.
NEAR TERM /THROUGH TONIGHT/
AS OF 230 AM TUESDAY...
...WINTER WEATHER ADVISORY FOR PORTIONS OF THE NW PIEDMONT INCLUDING
FORSYTH... DAVIDSON... AND GUILFORD COUNTIES THROUGH 500 AM
WEDNESDAY...
A MIGRATORY WEAK PARENT HIGH NEAR THE MASON-DIXON LINE WILL
CONTINUE TO SHIFT SOUTHEAST THIS MORNING...MOVING OFF THE
MID-ATLANTIC COAST BY MIDDAY. THIS WILL EFFECTIVELY SHUT-OFF
ANY REMAINING WEAK HORIZONTAL CAA FROM THE NORTH THIS MORNING AS
PRECIPITATION ASSOCIATED WITH MILLER B CYCLOGENESIS SPREADS EAST
INTO THE AREA. LOOKING AT UPSTREAM SATELLITE AND RADAR TRENDS OVER
TN... IT DOES APPEAR THAT THE EASTWARD PROGRESSION OF MEASURABLE
PRECIP IS SLOWING DOWN...BECOMING STRETCHED OUT IN A MORE
NORTH/SOUTH FASHION... ORIENTING ITSELF UNDERNEATH THE 110KT
NORTHERN STREAM JET STREAK OVER THE OHIO VALLEY AS THE SOUTHERN
STREAM OVER OK/TX/AR IS BECOMING SHEARED APART BY THE DOMINATE POLAR
VORTEX OVER THE NORTHERN PLAINS. OVER THE PAST 2 OR 3 MODEL
ITERATIONS...THE BIG 3 NWP MODELS... NAM/GFS/EC...HAVE DEFINITELY
TRIED TO SHOW THIS LATER ONSET OF PRECIP EAST OF THE MOUNTAINS.
DUE TO THE LATER ARRIVAL OF PRECIP...THE PROBABILITY OF ANY
FROZEN AND FREEZING PRECIP ACROSS THE NORTHERN AND NORTHWEST
PIEDMONT IS BECOMING LESS AND LESS...AS THE OVERALL MODEL CONSENSUS
IS TO QUICKLY RETREAT THE WET-BULB ZERO ACROSS THE FAR NW TIER BY
15Z...THE SAME TIME THAT THE SIGNIFICANT PRECIP IS EXPECTED TO
MOVE INTO THE AREA. BY 18Z...BOTH THE GFS AND NAM PARTIAL
THICKNESSES/P-TYPE NOMOGRAM INDICATE ALL RAIN...WITH THE BEST
LIFT/QPF OVERSPREADING THE AREA BETWEEN 18 TO 00Z. WILL KEEP
ADVISORY IN PLACE...LOWERING FROZEN(SNOW/SLEET) AND ICE
ACCUMULATIONS TO TRACE AMOUNTS.
THE ADVISORY AREA MAY ACTUALLY SEE A GREATER WINTER THREAT AS THE
SYSTEM/PRECIP STARTS TO PULL OUT THIS EVENING...POSSIBLY ENDING AS
FREEZING DRIZZLE AS THE COLD AND DRY AIR ALOFT OVERSPREADS THE AREA
WITH MODEL SOUNDINGS SHOWING INSUFFICIENT SATURATION IN THE
DENDRITIC GROWTH ZONE TO SUPPORT SNOW OR FLURRIES. WITH ADVISORY
GOING THROUGH 5 AM WEDNESDAY MORNING...THE ADVISORY AREA SHOULD BE
COVERED AS THE PRECIP LOOKS TO BE ENDING ACROSS THE AREA AOA 06Z. IT
IS POSSIBLE THAT THE ADVISORY MAY NEED TO BE EXTENDED EASTWARD
ACROSS THE NORTHERN PIEDMONT FOR ANY FREEZING DRIZZLE LATE THIS
EVENING. THE FREEZING DRIZZLE ALONG WITH RESIDUAL MOISTURE ON ROADS
COULD RESULT IN BLACK ICE AND DANGEROUS ROAD CONDITIONS WEDNESDAY
MORNING AS TEMPERATURES FALL INTO THE UPPER 20S WITH SKIES CLEARING
LATE.
SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/
AS OF 330 AM TUESDAY...
...HIGH WIND WATCH IN EFFECT FOR ALL OF CENTRAL NC ON
WEDNESDAY...
THE INTENSE MID LEVEL VORTEX... WITH HEIGHTS 3-4 STANDARD DEVIATIONS
BELOW NORMAL... CROSSES SOUTHERN VIRGINIA WEDNESDAY MORNING THROUGH
EARLY AFTERNOON AS A SURFACE LOW BOMBS JUST OFF THE NJ COAST.
THERE IS OVERWHELMING MODEL CONSENSUS OF A DEEP(DOWN TO 850MB)
STRATOSPHERIC OZONE INTRUSION WITHIN THE DRY SLOT AND ALONG THE
SOUTHERN/WESTERN QUADRANT OF THE CLOSED CYCLONE. WITH SOUNDINGS
SHOWING MIXING TO 775MB WEDNESDAY AFTERNOON...THIS INTRUSION
WILL LIKELY DRAG/MIX DOWN SOME OF THE 50 TO 60KT WINDS TO THE
SURFACE. WHILE A STRONGLY STABLE BL SHOULD CERTAINLY PREVENT FULL
REALIZATION OF THESE STRONG WINDS TO THE SFC...WIDESPREAD WIND GUSTS
OF 35 TO 40 MPH ARE EXPECTED...WITH THE POTENTIAL TO SEE SOME
LOCATIONS GUSTS OVER 40 MPH. WIND SPEEDS OF THIS MAGNITUDE ARE VERY
ALARMING CONSIDERING THE SATURATED/SOGGY SOILS ACROSS THE AREA...AS
TREE ROOTS WILL BE VERY VULNERABLE. COULD SEE WIDESPREAD WIND DAMAGE
FROM UPROOTED TREES. THUS WILL ISSUE A HIGH WIND WATCH FOR ALL OF
CENTRAL NC BEGINNING AT 6AM WEDNESDAY THROUGH 9PM.
WILL STAY ON THE COOL SIDE OF GUIDANCE FOR HIGHS WEDNESDAY...36-41
...WHICH AGREES WELL WITH LOCAL RESEARCH GIVEN THE LOW LEVEL DRY
ADIABATIC PROFILE. WIND CHILLS ARE LIKELY TO BE IN THE TEENS OVER
MUCH OF THE AREA AT LEAST THROUGH WEDNESDAY MORNING. WINDS REMAIN
VERY BRISK THROUGH MUCH OF WEDNESDAY NIGHT AS THE SURFACE CYCLONE
PULLS EAST AWAY FROM THE NORTHEAST COAST OVERNIGHT. LOWS 22-27.
LONG TERM /THURSDAY THROUGH MONDAY/
AS OF 240 AM TUESDAY...
OVERALL...THE LONG TERM PERIOD IS SHAPING UP TO BE DRY...WITH BELOW
NORMAL TEMPS...AS NORTHWESTERLY FLOW PERSISTS COURTESY OF A STRONG
POLAR VORTEX ACROSS EASTERN CANADA.
THURSDAY THROUGH FRIDAY: HIGH PRESSURE WILL BUILD IN FROM THE
NORTHWEST ON THURSDAY AS A STRONG LOW PRESSURE SYSTEM CONTINUES TO
MOVE NORTHEAST AWAY FROM THE CAROLINA COAST. THIS WILL RESULT IN AN
INCREASED PRESSURE GRADIENT WHICH WILL LEAD TO ANOTHER BREEZY DAY ON
THURSDAY (ALTHOUGH WINDS WILL BE WEAKER THAN EXPERIENCED ON
WEDNESDAY). MID/HIGH CLOUDS ARE EXPECTED TO INCREASE THROUGH FRIDAY
AS THE FLOW ALOFT PICKS UP AHEAD OF THE NEXT SYSTEM. THICKNESS
VALUES ARE PROGGED TO RANGE BETWEEN 1285-1295M...THEREFORE AM ONLY
EXPECTING HIGHS TO BE IN THE LOWER TO MID 40S...WITH LOWS IN THE
20S.
FRIDAY NIGHT THROUGH SATURDAY: A SOUTHERN STREAM WAVE IS PROGGED TO
TRACK ACROSS THE SOUTHEAST STATES FRIDAY NIGHT AND SHIFT OFFSHORE BY
MIDDAY SATURDAY. DURING THE SAME TIME FRAME...NORTHERN STREAM ENERGY
IS PROGGED TO DROP DOWN THROUGH THE DAKOTAS AND INTO THE
MIDWEST/OHIO VALLEY...SUPPRESSING THE SOUTHERN STREAM WAVE TO OUR
SOUTH. THEREFORE...THE TRACK OF THIS WAVE AND ITS ASSOCIATED SURFACE
LOW IS EXPECTED TO BE FAR ENOUGH SOUTH THAT CENTRAL NORTH CAROLINA
SHOULD REMAIN PRECIP FREE FROM THIS SYSTEM. IN FACT...MODELS
CONTINUE TO SHOW THE REGION REMAINING DRY WITH THIS SYSTEM...HOWEVER
A SLIGHT NORTHERN SHIFT OF THE TRACK COULD LEAD TO SOME LIGHT PRECIP
ACROSS THE SANDHILLS. FORECAST SOUNDINGS AND PARTIAL THICKNESS
VALUES INDICATE ANY PRECIP THAT WOULD FALL IN THIS REGION WOULD BE
IN THE FORM OF SNOW. HOWEVER...FOR NOW WILL SHOW A DRY FORECAST FOR
THIS PERIOD...BUT THIS WILL HAVE TO MONITORED CLOSELY OVER THE NEXT
COUPLE OF DAYS. TEMPS WILL REMAIN QUITE CHILLY...WITH LOWS REMAINING
IN THE 20S AND HIGHS GENERALLY IN THE UPPER 30S TO LOWER 40S.
SUNDAY THROUGH MONDAY: MORE DRY AND AND COLD WEATHER EXPECTED FOR
THIS PORTION OF THE FORECAST. HOWEVER...BOTH THE GFS AND ECMWF SHOW
A CLIPPER DROPPING ACROSS THE UPPER MIDWEST INTO THE OHIO VALLEY BY
MONDAY...ALTHOUGH THERE ARE SIGNIFICANT TIMING AND STRENGTH
DIFFERENCES. NEVERTHELESS...MODELS PROG MOST OF THE ENERGY TO REMAIN
NORTH OF THE REGION...THEREFORE WILL MAINTAIN THE DRY FORECAST AND
BELOW NORMAL TEMPS.
AVIATION /12Z TUESDAY THROUGH SATURDAY/
AS OF 630 AM TUESDAY...
CLOUDS WILL CONTINUE TO INCREASE AND LOWER EARLY THIS MORNING AHEAD
OF THE NEXT STORM SYSTEM. CEILINGS ARE EXPECTED TO FALL TO MVFR
DURING THE MID MORNING IN THE WEST WITH THESE CLOUDS LOWERING AND
SPREADING EAST AS THE DAY PROGRESSES. SOME SNOW OR SLEET WILL BE
POSSIBLE IN THE TRIAD AND ALONG THE VIRGINIA BORDER DURING THE MID
MORNING HOURS WHEN THE PRECIPITATION BEGINS. THIS AREA MAY ALSO
EXPERIENCE SOME LIGHT FREEZING RAIN LATER IN THE MORNING...WITH ALL
RAIN EXPECTED BY THE AFTERNOON. HOWEVER...CURRENT RADAR TRENDS
SUGGEST THAT THE PRECIP MAY START LATER THAN FIRST ANTICIPATED AND
THIS WOULD RESULT IN LESS WINTERY PRECIP DUE TO WARMER TEMPS AT THE
ONSET. ELSEWHERE ACROSS CENTRAL NORTH CAROLINA...ALL RAIN IS
EXPECTED. CEILINGS WILL FALL TO IFR IN MANY LOCATIONS DURING THE
AFTERNOON. ACROSS THE TRIAD...THERE COULD BE A BRIEF PERIOD OF
FREEZING DRIZZLE DURING THE EVENING HOURS AS TEMPS FALL. ALL PRECIP
IS EXPECTED TO END AROUND MIDNIGHT IN THE WEST...WITH PRECIPITATION
CLEARING THE EAST BY 09Z. CONDITIONS WILL SLOWLY IMPROVE ACROSS THE
REGION THROUGH SUNRISE.
VFR CONDITIONS WILL RETURN TO CENTRAL NORTH CAROLINA BY WEDNESDAY
MORNING. WEST TO WEST NORTHWEST WINDS OF 20 TO 35 MPH WITH GUSTS OF
45 MPH OR MORE ARE EXPECTED DURING THE DAY WEDNESDAY. THEN...VFR
CONDITIONS ARE EXPECTED WEDNESDAY THROUGH SATURDAY AS THE NEXT STORM
SYSTEM IS PROGGED TO TRACK SOUTH OF THE REGION.
HYDROLOGY
NUMEROUS RIVER FLOOD WARNINGS CONTINUE OVER CENTRAL NORTH
CAROLINA. WITH THE ABUNDANT SNOWFALL AND RAIN OVER THE LAST WEEK
AND A HALF (AROUND 2 TO 3 INCHES LIQUID EQUIVALENT OVER THE
ENTIRE AREA IN THE LAST 7 DAYS WITH POCKETS OF 3 TO 4 INCHES)...
SOILS REMAIN SATURATED. ALL AREA CREEKS AND STREAMS... INCLUDING
THOSE LACKING GAGES AND THEREFORE LACKING AN OFFICIAL RIVER
FORECAST... WILL CONTINUE TO RUN HIGH OVER THE NEXT WEEK AND
POSSIBLY LONGER. OUR NEXT STORM SYSTEM... ARRIVING EARLY TUESDAY
MORNING AND EXITING LATE TUESDAY NIGHT... IS EXPECTED TO BRING A
QUARTER TO HALF INCH OF PRECIPITATION... NOT A GREAT DEAL COMPARED
TO PREVIOUS SYSTEMS BUT THIS WILL STILL EXACERBATE THE SITUATION BY
SLOWING THE FALL OF RIVER AND CREEK LEVELS. PLEASE REFER TO THE
LATEST RIVER FLOOD STATEMENTS FOR DETAILED INFORMATION. -GIH
RAH WATCHES/WARNINGS/ADVISORIES
WINTER WEATHER ADVISORY FROM 5 AM TUESDAY TO 5 AM EST WEDNESDAY FOR
NCZ021-022-038.
HIGH WIND WATCH FROM WEDNESDAY MORNING THROUGH WEDNESDAY EVENING FOR
NCZ007>011-021>028-038>043-073>078-083>086-088-089.
SYNOPSIS...CBL
NEAR TERM...CBL
SHORT TERM...CBL/HARTFIELD
LONG TERM...KRR
HYDROLOGY...HARTFIELD
AVIATION...KRR
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