624
FXUS64 KJAN 172040
AFDJAN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
340 PM CDT WED OCT 17 2018
DISCUSSION
THIS EVENING THROUGH TOMORROW:
THROUGH THIS AFTERNOON, A FEW LIGHT RAIN SHOWERS WILL BE POSSIBLE
AS MID-LEVEL MOISTURE IS LIFTED OVER THE COOLER SURFACE AIRMASS.
DRIER AIR WILL CONTINUE TO SLOWLY WORK SOUTHWARD INTO OUR FORECAST
AREA, FURTHER ERODING THE LOW STRATUS ACROSS THE REGION AND
ENDING RAIN CHANCES. BREAKS IN THE CLOUDS ARE ALREADY APPARENT AS
FAR SOUTH AS INTERSTATE 20. EXPECT TONIGHT'S LOW TEMPERATURES TO
RANGE FROM THE LOWER 50S IN OUR NORTH TO THE UPPER 50S IN THE PINE
BELT. TEMPERATURES WILL REBOUND SOME TOMORROW WITH BROKEN CLOUD
COVER AND INCREASED DAYTIME HEATING. NO PRECIPITATION IS EXPECTED
TOMORROW. /NF/
TOMORROW NIGHT THROUGH WEDNESDAY:
A SEASONABLY ACTIVE FALL WEATHER PATTERN WILL CONTINUE THROUGH
THE PERIOD WITH THE PASSAGE OF ANOTHER COLD FRONT FOLLOWED BY A
COUPLE SOUTHERN STREAM DISTURBANCES. BY TOMORROW NIGHT, THE CUTOFF
LOW OVER THE DESERT SOUTHWEST WILL BEGIN TO FILL AS IT LIFTS TO
THE NORTHEAST AND BECOMES ABSORBED INTO THE NORTHERN STREAM. SUB-
TROPICAL RIDGING WILL ALSO EXTEND FROM THE GULF COAST STATES TO
JUST NORTH OF THE BAHAMAS. CYCLONIC ROSSBY WAVE BREAKING OVER THE
GULF OF ALASKA WILL HELP ESTABLISH A BRIEF DIPOLE BLOCKING PATTERN
OVER THE WEST COAST ON FRIDAY WHICH WILL AMPLIFY A DIGGING TROUGH
DIVING INTO THE NORTHERN PLAINS. THIS TROUGH WILL SUPPRESS THE
SUB-TROPICAL RIDGING AND WILL SEND A COLD FRONT THROUGH THE GREAT
PLAINS TOWARDS THE ARKLAMISS REGION. HOWEVER, TEMPERATURES WILL
BE WARM ON FRIDAY BEFORE THE RIDGE IS ABLE TO GET FULLY DISPLACED,
WITH THE WARMEST HIGHS IN THE LOW 80S EXPECTED SOUTHEAST OF THE
NATCHEZ TRACE CORRIDOR. SOUTHWESTERLY FLOW AROUND THE WESTERN EDGE
OF THE RETREATING RIDGE WILL HELP FOSTER SCATTERED SHOWERS ACROSS
THE AREA, ESPECIALLY IN THE VICINITY OF THE APPROACHING FRONTAL
BOUNDARY. THE COLD FRONT WILL MAKE ITS WAY THROUGH THE AREA FRIDAY
NIGHT THROUGH SATURDAY WITH MAINLY SCATTERED SHOWERS EXPECTED AS
THE BEST FORCING AND UPPER DYNAMICS FROM THE PARENT TROUGH REMAIN
DISPLACED TO THE NORTH.
THE BULK OF THE COOLER AND DRIER AIR WILL MOVE IN SATURDAY NIGHT
WITH COLD AIR ADVECTION RAMPING UP AS A MODIFIED CONTINENTAL POLAR
AIRMASS ORIGINATING FROM THE CANADIAN YUKON DROPS THROUGH THE PLAINS
AND INTO THE MISSISSIPPI RIVER VALLEY. THE COLDEST MORNING OF THE
SEASON SO FAR WILL LIKELY BE ON MONDAY AS THE SURFACE RIDGE AXIS
BECOMES CENTERED FROM THE MID-ATLANTIC INTO THE DEEP SOUTH. THIS
WILL RELAX THE SURFACE PRESSURE GRADIENT WITH LIGHT TO CALM WINDS
AND DRY AIR WITH SURFACE DEWPOINTS IN THE LOW 40S TO UPPER 30S
CONDUCTIVE FOR EFFICIENT RADIATIONAL COOLING. THE MAIN LIMITING
FACTOR WILL BE UNCERTAINTY REGARDING CLOUD COVER FROM CIRRUS AS A
PERTURBATION EMBEDDED IN THE WESTERLY SOUTHERN STREAM FLOW
APPROACHES THE ARKLAMISS. HOWEVER, LATEST GLOBAL MODELS HAVE SLOWED
DOWN THE TIMING OF THIS FEATURE AND CLOUD COVER LOOKS TO HOLD OFF
UNTIL LATE ENOUGH ON MONDAY MORNING TO NOT OVERLY HINDER RADIATIONAL
COOLING POTENTIAL. WITH THAT BEING SAID, LOW TEMPERATURES ARE
PROGGED TO DROP INTO THE UPPER 30S TO MID 40S ACROSS THE REGION.
HEADING INTO EARLY NEXT WORK WEEK, THERE ARE INDICATIONS THAT
SEVERAL SOUTHERN STREAM DISTURBANCES COULD INTERACT WITH THE
NORTHERN GULF BAROCLINIC ZONE AND HELP INDUCE SEVERAL SURFACE WAVES.
THE FIRST OF THESE DISTURBANCES IS PROGGED TO REMAIN SUPPRESSED
BENEATH SHORTWAVE RIDGING ON TUESDAY WITH HEAVY RAINFALL ALONG AND
JUST OFF THE GULF COAST. HOWEVER, A MORE PRONOUNCED SHORTWAVE TROUGH
IS EXPECTED TO MOVE OUT OF NORTHERN MEXICO INTO SOUTHERN TEXAS AND
COULD BRING INCREASED RAIN CHANCES TO THE ARKLAMISS REGION BY THE
MIDDLE OF NEXT WEEK. /TW/
AVIATION
18Z TAF DISCUSSION:
VFR CONDITIONS WILL PREVAIL AT KGLH, GWO, AND KGTR THROUGH THE
PERIOD. TAF SITES THROUGH CENTRAL AND SOUTHERN MISSISSIPPI WILL
BEGIN THE PERIOD WITH IFR CEILINGS DUE TO A PERSISTENT LOW STRATUS
DECK. THESE CEILINGS ARE EXPECTED TO LIFT TO MVFR HEIGHTS BY 21Z
AT THOSE TAF SITES, AND IMPROVE TO VFR CONDITIONS BY 00Z THURSDAY.
LIGHT RAIN SHOWERS WILL CONTINUE AROUND THE REGION BEFORE 00Z,
CAUSING BRIEF PERIODS OF REDUCED VISIBILITY SHOULD THEY IMPACT ANY
TAF SITE. /NF/
PRELIMINARY POINT TEMPS/POPS
JACKSON 56 71 56 81 / 5 2 0 7
MERIDIAN 54 72 55 82 / 5 1 0 6
VICKSBURG 55 70 54 78 / 5 1 0 8
HATTIESBURG 59 76 59 85 / 5 0 0 18
NATCHEZ 57 72 58 82 / 5 3 0 11
GREENVILLE 51 66 51 70 / 5 1 0 16
GREENWOOD 51 67 52 74 / 5 1 0 11
JAN WATCHES/WARNINGS/ADVISORIES
MS...NONE.
LA...NONE.
AR...NONE.
TW/NF
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