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Area Forecast Discussion

240
FXUS62 KCHS 051544
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1044 AM EST FRI FEB 5 2016

.SYNOPSIS...
COOL CONTINENTAL HIGH PRESSURE WILL BUILD OVER THE REGION
TODAY...FOLLOWED BY A DEVELOPING COASTAL TROUGH SATURDAY. LOW
PRESSURE WILL THEN DEVELOP AND DEEPEN OFF THE SOUTHEAST COAST
SUNDAY AND MOVE WELL TO THE NORTHEAST MONDAY. A DEEP TROUGH WILL
THEN BE IN PLACE THROUGH THE MIDDLE OF NEXT WEEK...BRINGING COOL
CONDITIONS TO THE AREA.

&&

.NEAR TERM /THROUGH TONIGHT/...
TODAY...WITH THE PASSAGE OF A POTENT TROUGH ALOFT EARLY THIS
MORNING THE ATMOSPHERE HAS BECOME BONE DRY...A FAR CRY FROM
YESTERDAY WHEN PWATS WERE SOME 3 STANDARD DEVIATIONS ABOVE NORMAL
WHILE TODAY THEY`LL BE 2-3 STANDARD DEVIATIONS BELOW NORMAL.
WE`RE LOOKING AT FULL SUNSHINE AS A 1033 MB HIGH BUILDS FROM THE
LOWER AND MIDDLE MS VALLEY. DESPITE THIS OUR TEMPS WILL STRUGGLE
TO GET OUT OF THE 40S...AND WITH 850 MB TEMPS AROUND MINUS 1C
SOUTH TO MINUS 3C NORTH WE ARE FORECASTING NOTHING MORE THAN NEAR
50 FAR NORTH TO THE LOWER AND MIDDLE 50S ELSEWHERE. GIVEN A LOT OF
RAIN THE PAST TWO DAYS A GOOD PART OF THE SUN`S ENERGY WILL BE
SPENT EVAPORATING THE STANDING WATER THAT PERSISTS. THUS, WE
MIGHT BE A LITTLE OPTIMISTIC ON MAX TEMPS THIS AFTERNOON.

STEADY ISALLOBARIC PRESSURE RISES AND COLD ADVECTION THIS MORNING
AND EARLY AFTERNOON WILL GENERATE BREEZY TO WINDY NW AND NORTH
WINDS THAT AVERAGE 20-25 MPH SUSTAINED AND GUSTS OF 30-35 MPH. NOT
QUITE WIND ADVISORY CRITERIA, BUT ENOUGH TO MAKE IT FEEL CHILLY
COMPARED TO THE PAST SEVERAL DAYS. WINDS WILL GRADUALLY SUBSIDE
DURING THE AFTERNOON...DROPPING TO LESS THAN 15 MPH FOR MOST OF US
BY 3 OR 4 PM.

LAKE WINDS...THE LAKE WIND ADVISORY HAS BEEN CANCELLED BECAUSE
WIND GUSTS HAVE EASED WELL BELOW 25 KT (29 MPH).

TONIGHT...THE CORE OF THE COLD AIR SITS ATOP THE AREA AS SURFACE
HIGH PRESSURE ELONGATES SW TO NE OVER THE SE QUADRANT OF THE
COUNTRY. WINDS WILL DECOUPLE QUICKLY WITH SUNSET THIS
EVENING...AND MANY INLAND LOCATIONS WILL GO NEAR OR AT CALM
CONDITIONS. THIS WILL SET THE STAGE FOR EXCELLENT RADIATIONAL
COOLING UNDER CLEAR SKIES AND THE DRY AIR MASS. THIS ALLOWS FOR
LOWS IN THE UPPER 20S AND LOWER 30S INLAND FROM THE INTRA-COASTAL.
ALONG THE COAST THERE IS JUST ENOUGH OF A GRADIENT TO PERSIST WITH
A NORTH/NE SYNOPTIC FLOW...AND THIS MIXING WILL HOLD TEMPS IN THE
MIDDLE AND UPPER 30S.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
SATURDAY AND SATURDAY NIGHT...THE PATTERN ALOFT WILL FEATURE A SHARP
SOUTHERN STREAM SHORTWAVE THAT IS PROGGED TO DIVE ACROSS THE LOWER
MISSISSIPPI VALLEY AND TRACK ALONG THE GULF COAST INTO SUNDAY
MORNING. MEANWHILE...A 120 KT 300 MB JET WILL PUSH ACROSS THE
NORTHERN GULF OF MEXICO AND OFF THE SOUTHEAST COAST...AND DIVERGENCE
IN ITS RIGHT ENTRANCE REGION WILL EVENTUALLY HELP TO DRIVE THE
DEVELOPMENT OF A SURFACE LOW OFF THE FLORIDA COAST. MOISTURE WILL
INCREASE FROM THE SOUTH DURING THE DAY AND OVERNIGHT...THOUGH MOST
OF THE MORE SIGNIFICANT MOISTURE WILL REMAIN OVER THE COASTAL
WATERS. A SURFACE TROUGH WILL HELP TO KICK OFF LIGHT RAINS/SHOWERS
OVER THE WATERS DURING THE DAY ON SATURDAY. THEN LATE IN THE DAY AND
MAINLY OVERNIGHT THE WESTERN PERIPHERY OF THE EXPANDING
PRECIPITATION SHIELD WILL PUSH INLAND...ESPECIALLY ALONG THE SOUTH
CAROLINA COAST. THE POP GRADIENT WILL LIKELY BE VERY TIGHT...AND THE
AREA THAT STANDS THE BEST CHANCE TO GET RAINFALL IS THE REGION FROM
BEAUFORT COUNTY TO COLLETON COUNTY AND THE TRI-COUNTY. POPS HAVE
BEEN LIMITED STILL IN THE LIKELY RANGE AS THE INLAND EXTENT OF THE
PRECIPITATION WILL BE CLOSELY TIED TO THE PROXIMITY TO THE COAST OF
THE DEVELOPING LOW. THERE IS STILL A GOOD CHANCE THAT THE LOW
DEVELOPS FURTHER OFFSHORE...WHICH WOULD SIGNIFICANTLY SHRINK THE
SIZE OF THE AREA THAT WOULD SEE RAINFALL. THE LAST THING TO MENTION
WITH THIS SYSTEM IS FOR LATE SATURDAY NIGHT AS THE PRECIPITATION
ENDS. MODELS SHOW COOLER AIR WRAPPING INTO THE REGION AROUND THE
OFFSHORE LOW...AND THERE IS A LOW END CHANCE ANY LINGERING RAINFALL
COULD TRANSITION TO FLURRIES OR EVEN LIGHT SNOW. CONFIDENCE IS LOW
IN THIS SCENARIO AND NO ACCUMULATIONS ARE EXPECTED. SATURDAY WILL BE
A COOL DAY WITH HIGHS ONLY REACHING THE LOW 50S. LOWS WILL FALL INTO
THE LOW 30S INLAND...RANGING TO THE MID/UPPER 30S AT THE COAST.

SUNDAY THROUGH MONDAY...ANY LINGERING PRECIPITATION WILL QUICKLY
COME TO AN END SUNDAY MORNING AS THE OFFSHORE LOW TRACKS OFF TO THE
NORTHEAST. THEN INTO MONDAY...A DEEP AND COLD TROUGH WILL CARVE OUT
ACROSS THE GREAT LAKES AND INTO THE SOUTHEAST. THIS WILL DRIVE A
MOSTLY DRY AREA OF LOW PRESSURE FROM WEST TO EAST WELL NORTH OF THE
FORECAST AREA. THERE IS JUST ENOUGH MOISTURE RETURN WITH THIS SYSTEM
THAT WE COULD SEE A FEW VERY LIGHT SHOWERS MONDAY AFTERNOON...THOUGH
THE BULK OF ANY ACTIVITY WILL REMAIN TO THE NORTH. CARRYING A SLIGHT
CHANCE POP HAS SUPPORT FROM THE AVAILABLE MODEL GUIDANCE...SO IT HAS
BEEN ADDED TO THE FORECAST. RAINFALL AMOUNTS...IF ANY...WILL BE VERY
LIGHT. COOL TEMPERATURES WILL CONTINUE...RUNNING 5-10 DEGREES BELOW
NORMAL.

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
OVERALL THE LONG TERM PERIOD LOOKS RATHER STEADY STATE AND COOL. THE
DEEP AND COLD TROUGH IN THE MID/UPPER LEVELS WILL PERSIST AND EVEN
GET REINFORCED BY ADDITIONAL ENERGY DIVING OUT OF THE NORTHERN
PLAINS INTO MID WEEK. THIS SET UP WILL KEEP TEMPERATURES COOL AND
WELL BELOW NORMAL WITH BREEZY CONDITIONS EACH AFTERNOON. HIGH
PRESSURE WILL SETTLE INTO THE REGION FROM THE CENTRAL CONUS BY ABOUT
THURSDAY. FOR MUCH OF THE PERIOD HIGHS WILL STRUGGLE TO GET OUT OF
THE 40S WITH OVERNIGHT LOWS INTO THE 20S AWAY FROM THE COAST.
ALSO...THERE ARE NO SIGNIFICANT OPPORTUNITIES FOR RAIN.

&&

.AVIATION /16Z FRIDAY THROUGH TUESDAY/...
THROUGH 12Z SATURDAY...VFR AT KCHS AND SAV. SURFACE WINDS WILL BE
GUSTY THROUGH MUCH OF THE DAYLIGHT HOURS...PEAKING AT 25-30 KT
INTO THE EARLY AFTERNOON.

EXTENDED AVIATION OUTLOOK...THERE WILL BE A CHANCE FOR RESTRICTED
CEILINGS LATE SATURDAY NIGHT AND EARLY SUNDAY MORNING. OTHERWISE
VFR CONDITIONS WILL PREVAIL.

&&

.MARINE...
TODAY...TREACHEROUS MARINE CONDITIONS WILL PREVAIL IN RESPONSE TO
A TIGHT SURFACE PRESSURE GRADIENT IN THE WAKE OF DEEPENING LOW
PRESSURE NEAR CAPE HATTERAS AND CONTINENTAL HIGH PRESSURE BUILDING FROM
THE WEST. SMALL CRAFT ADVISORIES REMAIN IN EFFECT FOR THE
CHARLESTON HARBOR AND ALL OF THE WATERS WITHIN 20 NM WATERS FROM
THE SANTEE RIVER TO THE ALTAMAHA SOUND. BUOY 41008 IS BARELY
REPORTING GUSTS TO 25 KT THIS MORNING AND THAT WOULD INTERPOLATE
TO GUSTS UNDER 20 KT ACROSS THE OUTER GEORGIA WATERS. AS A RESULT,
DROPPED THE GALE WARNING FOR THAT AREA AND ISSUED A SMALL CRAFT
ADVISORY. SEAS REMAIN IN THE 4-7 FOOT RANGE WITHIN 20 NM OF THE
COAST AND 8-10 FT ACROSS THE OUTER GEORGIA WATERS WHERE A BETTER
FETCH WILL PREVAIL. WINDS AND SEAS WILL GRADUALLY TREND DOWNWARD THIS
AFTERNOON AS THE PRESSURE GRADIENT WEAKENS...COLD ADVECTION SHUTS
OFF AND PRESSURE RISES SLOW. THE ADVISORIES SHOULD PERSIST INTO
EARLY EVENING WITHIN 20 NM AND MUCH LONGER FOR THE OUTER GEORGIA
WATERS.

TONIGHT...THERE IS SUBTLE IMPROVEMENT IN CONDITIONS EARLY ON AS
HIGH PRESSURE BUILDS OVER THE SE STATES AND THERE IS A FURTHER
RELAXATION TO THE GRADIENT. HOWEVER...THE GRADIENT STARTS TO
TIGHTEN AGAIN OVERNIGHT AS A WEAK COASTAL TROUGH STARTS TO FORM
NEARBY. NORTH WINDS WILL CLOCK AROUND TO THE NE AND SPEEDS WILL
BEGIN TO INCREASE AGAIN. THE SMALL CRAFT ADVISORY WILL REMAIN UP
FOR THE OUTER GEORGIA WATERS.

SATURDAY THROUGH WEDNESDAY...OVERALL MARINE CONDITIONS ARE
EXPECTED TO BE LESS THAN IDEAL THIS WEEKEND AND INTO EARLY NEXT
WEEK. THE FIRST PERIOD OF POOR CONDITIONS WILL BEGIN TO RAMP UP
SATURDAY AND SATURDAY NIGHT AS AN AREA OF LOW PRESSURE DEVELOPS
OFFSHORE AND WINDS INCREASE IN THE TIGHTENING PRESSURE GRADIENT.
SOLID SMALL CRAFT ADVISORY CONDITIONS WILL RAMP UP ESPECIALLY
SATURDAY NIGHT...AND WILL CONTINUE THROUGH MUCH OF THE DAY ON
SUNDAY. CONDITIONS WILL THEN BRIEFLY IMPROVE SUNDAY NIGHT BEFORE
DETERIORATING AGAIN LATE ON MONDAY AND CONTINUING THROUGH MONDAY
NIGHT/TUESDAY BEHIND THE PASSAGE OF A FAST MOVING COLD FRONT.
ANOTHER ROUND OF SOLID SMALL CRAFT ADVISORY CONDITIONS CAN BE
EXPECTED...WITH A NARROW TIME WINDOW WHERE GALES COULD OCCUR OVER
THE OUTER GEORGIA WATERS MONDAY NIGHT.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR AMZ330.
     SMALL CRAFT ADVISORY UNTIL 7 PM EST THIS EVENING FOR AMZ350-
     352-354.
     SMALL CRAFT ADVISORY UNTIL 7 AM EST MONDAY FOR AMZ374.

&&

$$
SYNOPSIS...
NEAR TERM...
SHORT TERM...
LONG TERM...BSH
AVIATION...
MARINE...



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