504
FXUS64 KHUN 181551
AFDHUN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
1051 AM CDT THU OCT 18 2018
NEAR TERM
(REST OF TODAY)
ISSUED AT 1051 AM CDT THU OCT 18 2018
MORNING SURFACE ANALYSIS SHOWS A BROAD AREA OF HIGH PRESSURE OVER THE
MIDWEST AS THE MAIN INFLUENCE ON TN VALLEY WEATHER, BUT MODEL
INITIALIZATIONS CONTINUE TO SHOW AN EXTENDED WEST-EAST ORIENTED SHEAR
AXIS DRAPED ACROSS THE REGION AS WELL. GOES-EAST IMAGERY SHOWS A
BAND OF PERSISTENT MID/HIGH-LEVEL CLOUDINESS ACCOMPANYING THIS
FEATURE, OVER THE TN VALLEY AT LEAST. BETWEEN WEAK PERSISTENT COLD
AIR ADVECTION AND THE CONTINUED CLOUD COVER, TEMPERATURES HAVE
LARGELY REMAINED IN THE MID-UPPER 50S; ONLY A FEW SITES RECEIVING
MORE SUNSHINE HAVE RISEN INTO THE THE 60S.
MOISTURE WILL REMAIN CONFINED TO THE MID AND UPPER LEVELS THROUGH
TODAY, SO A DRY FORECAST STILL LOOKS GOOD. THE FORECAST HAS BEEN
UPDATED TO INCREASE CLOUD COVER FOR A LONGER PERIOD OF TIME, MORE IN
LINE WITH THE GFS AND BLENDED GUIDANCE PROGS. THIS MAY INHIBIT
TEMPERATURES A LITTLE MORE THAN THE CURRENT HIGH FORECAST (MID-UPPER
60S) SUGGESTS, SO TEMPERATURES WILL BE NUDGED DOWN SLIGHTLY.
SHORT TERM
(TONIGHT THROUGH SATURDAY NIGHT)
ISSUED AT 307 AM CDT THU OCT 18 2018
THE SURFACE HIGH WILL MOVE OFF OF THE MID ATLANTIC COAST LATER
TONIGHT, WITH SURFACE FLOW BECOME MORE SOUTHERLY. MEANWHILE, THE AXIS
OF THE UPPER RIDGE WILL BUILD AGAIN INTO THE AREA, KEEPING SOME FLOW
OF MOISTURE ACROSS THE TN VALLEY. DESPITE THE RETURN FLOW SETTING UP
OVERNIGHT, TEMPERATURES WILL STILL BE ABLE TO COOL QUITE A BIT, WITH
LOWS BOTTOMING OUT IN THE UPPER 40S TO LOWER 50S. THE UPPER RIDGE
AXIS WILL MOVE EAST OF THE AREA DURING THE DAY FRIDAY AS A
PROGRESSIVE TROUGH EJECTS INTO THE PLAINS. AS FLOW BECOMES SOUTHERLY
THROUGH THE VERTICAL COLUMN, PW VALUES WILL CLIMB ABOVE 1.5 INCHES
BY FRIDAY AFTERNOON. THIS WILL RESULT IN AN INCREASE IN CLOUD COVER,
BUT NOT BEFORE TEMPS REACH INTO THE MID 70S.
A COLD FRONT, ASSOCIATED WITH THE AFOREMENTIONED UPPER TROUGH, WILL
BE JUST ON THE DOORSTEP OF THE TN VALLEY BY SUNSET ON FRIDAY AND THEN
QUICKLY MOVE TO THE EAST THROUGH THE OVERNIGHT HOURS. WITH AN
ABUNDANCE OF MOISTURE AND PLENTY OF LIFT, NUMEROUS TO WIDESPREAD
SHOWERS WILL SHIFT EASTWARD ACROSS THE AREA, WITH THE HIGHEST
COVERAGE EXPECTED TO BE JUST BEHIND THE FRONT. THE FRONT WILL BE WELL
SOUTH OF THE AREA BY DAYBREAK ON SATURDAY, WITH THE POST-FRONTAL
RAINFALL SLOWLY EXITING THE AREA DURING THE MID MORNING HOURS. THE
AIRMASS BEHIND THE FRONT WILL BE QUITE COLD AND DRY, WITH THE DRIER
AIR QUICKLY FILTERING IN DURING THE AFTERNOON. THE COMBINATION OF
COLD AIR ADVECTION AND LINGERING CLOUD COVER DURING THE DAYLIGHT
HOURS WILL KEEP HIGHS IN THE LOWER TO MID 60S. CLOUDS WILL THEN
DECREASE OVERNIGHT AS THE UPPER FLOW BECOMES NORTHWESTERLY. THE
ASSOCIATED SURFACE HIGH WILL BE FAIRLY STRONG AS IT BUILDS
SOUTHEASTWARD INTO THE AREA. THIS WILL KEEP THE PRESSURE GRADIENT
FAIRLY TIGHT OVERNIGHT AND WINDS WILL NOT REALLY DROP OFF. WHILE THIS
MEANS RADIATIONAL COOLING WILL NOT BE FAIRLY STRONG, THE COLD AIR
ADVECTION WILL BE AND THUS OVERNIGHT LOWS WILL DROP INTO THE UPPER
30S TO LOWER 40S. FROST DOES NOT APPEAR LIKELY SATURDAY NIGHT, GIVEN
THE WINDS AND DEWPOINT DEPRESSIONS GREATER THAN 5 DEGREES.
LONG TERM
(SUNDAY THROUGH WEDNESDAY)
ISSUED AT 307 AM CDT THU OCT 18 2018
THE RIDGE BUILDING IN THE SOUTHERN PLAINS UP INTO THE INTERMOUNTAIN
WEST WILL PUSH A TROUGH ACROSS NEW ENGLAND THIS WEEKEND. THIS WILL
ALLOW FOR A SFC HIGH IN THE MIDWEST TO BUILD INTO THE REGION SUNDAY
AND MONDAY. THE DECREASING CLOUD COVER AND LIGHT WINDS WILL ALLOW FOR
GOOD RADIATIONAL COOLING GETTING TEMPS DOWN INTO THE UPPER 30S! THIS
WILL ALSO GIVE WAY TO THE POTENTIAL FOR PATCHY FROST ACROSS SOUTHERN
MIDDLE TN AND HIGHER ELEVATIONS IN NE AL EARLY MONDAY MORNING.
DAYTIME HIGHS ON SUNDAY WILL BE IN THE UPPER 50S, WARMING UP INTO THE
LOWER 60S ON MONDAY DUE TO SOUTHEASTERLY WINDS. THIS WILL MOVE IN
SOME CLOUD COVER MONDAY NIGHT, AND KEEP OVERNIGHT LOWS IN THE UPPER
40S.
A TROUGH WILL SLIDE INTO THE GREAT LAKES ON TUESDAY, SLOWING DOWN THE
EASTWARD PROGRESSION OF THE RIDGE. THE SFC HIGH WILL BE PUSHED INTO
THE MID ATLANTIC BY TUESDAY AFTERNOON, KEEPING CONDITIONS DRY FOR ONE
MORE DAY. DAYTIME HIGHS WILL BE A TAD WARMER IN THE UPPER 60S. MODELS
DIVERGE FOR THE REST OF THE EXTENDED FORECAST. A SERIES OF WEAK
DISTURBANCES WILL GLIDE UP THE SOUTHWESTERLY FLOW INTO THE REGION
AND GIVE WAY TO A ISO/SCT SHOWERS WEDNESDAY AFTERNOON AND EVENING.
THE ECMWF KEEPS THE TROUGH LINGERING OVER THE GREAT LAKES ON
WEDNESDAY, FURTHER SLOWING DOWN THE RIDGE WHICH WILL IN TURN WEAKEN A
SFC LOW COMING UP OUT OF TX AND QUICKLY SLIDE IT RIGHT OVER AL IN
SEMI- ZONAL FLOW. THE GFS ON THE OTHER HAND LETS THE TROUGH EXIT
QUICKLY, PROGRESSES THE RIDGE AND HAS A STRONGER, SLOWER SFC LOW LIFT
JUST NW OF THE TN VALLEY. BOTH SOLUTIONS WILL BRING RAINFALL FOR THE
TN VALLEY WEDNESDAY NIGHT AND THURSDAY, HOWEVER THE RAINFALL
COVERAGE AND AMOUNTS WILL VARY DEPENDING ON THE SOLUTION YOU FAVOR.
WITH THIS IN MIND, STAYED CLOSE TO THE BLEND.
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 600 AM CDT THU OCT 18 2018
VFR CONDITIONS WILL PREVAIL AT THE KMSL AND KHSV TERMINALS THROUGH
THE PERIOD. OTHER THAN PASSING HIGH CLOUDS, SKIES WILL REMAIN MOSTLY
CLEAR. WINDS WILL GENERALLY BE FROM THE NORTHEAST, BETWEEN 7 AND
10KTS DURING THE DAY AND BECOME LIGHT OVERNIGHT.
HUN WATCHES/WARNINGS/ADVISORIES
AL...NONE.
TN...NONE.
NEAR TERM...BCC
SHORT TERM...73
LONG TERM...JMS
AVIATION...73
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