000
FXUS64 KSJT 171112
AFDSJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN ANGELO TX
612 AM CDT FRI MAY 17 2013

.DISCUSSION...
SEE THE 12Z AVIATION DISCUSSION BELOW.

&&

.AVIATION...
IFR VSBYS WITH MVFR CIGS ARE SKIRTING THE NORTHERN AND EASTERN
BOUNDARIES OF THE CWA AREAS THIS MORNING BUT ARE NOT EXPECTED TO
AFFECT ANY OF THE FORECAST TERMINALS. THESE CLOUDS WILL ERODE
QUICKLY AFTER MIXING COMMENCES...LEAVING A FEW ALTOCU THROUGH
EARLY AFTERNOON. THE DRYLINE WILL MIX EAST THIS AFTERNOON AND IS
EXPECTED TO STALL ROUGHLY FROM KBWD TO KJCT. VERY ISOLATED DIURNAL
CONVECTION IS EXPECTED BETWEEN 21-02Z WITH KBBD AND KJCT REALLY
BEING THE ONLY TERMINALS IN PLAY. HOWEVER...CONFIDENCE IS LESS
THAN 10 PERCENT THAT EITHER TERMINAL WILL BE AFFECTED SO NO
MENTION WILL BE MADE AT THIS TIME. OTHERWISE...EXPECT A HIGH BASED
CU FIELD IN THE VICINITY OF THE DRYLINE. SOUTHWEST WINDS OF 10-15
KTS THIS MORNING WILL BACK TO THE SOUTHEAST BY LATE AFTERNOON.
GUSTY CONDITIONS ARE EXPECTED OVERNIGHT AT KABI AS THE LOW LEVEL
JET INTENSIFIES.

JOHNSON

&&

.PREV DISCUSSION... /ISSUED 419 AM CDT FRI MAY 17 2013/

SHORT TERM...
THE BIG STORY IN THE SHORT TERM IS THE POTENTIAL FOR RECORD HIGH
TEMPERATURES THIS AFTERNOON. TODAY WILL BE THE HOTTEST DAY OF
THE YEAR THUS FAR...HOPEFULLY NOT A HARBINGER OF THINGS TO COME
OVER THE NEXT FEW MONTHS. A LOOK AT THE SYNOPTIC PATTERN SHOWS A
SLOW MOVING TROUGH OVER THE WEST COAST AND A COMPACT CLOSED
CYCLONE MOVING ACROSS THE CENTRAL MISSISSIPPI RIVER VALLEY.
BETWEEN THESE TWO FEATURES OVER THE PLAINS...WE SEE A BUILDING
SHORTWAVE RIDGE. DRILLING DOWN A BIT MORE...THE WATER VAPOR LOOP
INDICATES A SUBTLE SHORTWAVE TROUGH MOVING ACROSS WESTERN NORTH
TX. THIS IS RESPONSIBLE FOR THE ELEVATED CONVECTION DEVELOPING
OVER CENTRAL TX AT THIS TIME. ANOTHER WAVE IS LOCATED OVER
NORTHWEST MEXICO...POISED TO LIFT NORTHEAST ACROSS THE SOUTHERN
PLAINS IN THE NEXT 24 HRS.

THE LOWER TROPOSPHERIC THERMAL RIDGE IS ANOMALOUSLY WARM...
YIELDING H85 TEMPS NEAR 30C AS OF 00Z. SIMILAR WARMTH IN THE
LOW/MID LEVELS IS ANTICIPATED AGAIN TODAY...ALTHOUGH THE THERMAL
RIDGE WILL EXPAND TO THE NORTH AND EAST. THIS WILL SUPPORT MAX
TEMPS OF 100 TO 105 DEGREES ACROSS ALL OF WEST CENTRAL TX. I THINK
SOME AREAS OF THE CONCHO VALLEY /INCLUDING SAN ANGELO/ MAY REACH
AS HIGH AS 106 DEGREES. THE DRYLINE WILL MIX EAST THIS AFTERNOON
AND IS FORECAST TO STALL NEAR A BROWNWOOD TO JUNCTION LINE. WEST
OF THE DRYLINE...DEWPOINTS WILL FALL TO NEAR 40 DEGREES.
HOWEVER...TO THE EAST I EXPECT DEWPOINTS TO HOLD IN THE MID 50S.
GIVEN THE INTENSE SURFACE HEATING...WE SHOULD BE ABLE TO BREAK THE
CAP ALONG THE DRYLINE... ALLOWING VERY ISOLATED CONVECTION BY LATE
AFTERNOON. THE HIRES CAMS /AND EVEN THE NAM AND GFS/ HINT AT THIS
OCCURRING. RAP/NAM POINT SOUNDINGS BOTH DEPICT NO CAP LEFT BY 22Z
WITH PROGGED MLCAPE VALUES APPROACHING 3000 J/KG OVER THE FAR
EASTERN COUNTIES. DEEP LAYER SHEAR /0-6 KM/ IS PROGGED TO BE 25-35
KTS WHICH COULD SUPPORT SOME ORGANIZED STORMS. THUS...THE THREAT
FOR LARGE HAIL AND GUSTY WINDS CANNOT BE RULED OUT...ALTHOUGH THE
THREAT IS HIGHLY DEPENDENT ON THE CAP BREAKING AND WOULD BE VERY
ISOLATED AT BEST.

TONIGHT...ANY ONGOING CONVECTION WILL LAST UNTIL AROUND 9 PM
BEFORE DISSIPATING WITH THE LOSS OF DAYTIME HEATING. A STRONG
LOW LEVEL JET WILL DEVELOP IN RESPONSE TO THE SUBGEOSTROPHIC WINDS
OBSERVED WITHIN THE VERY DEEP BOUNDARY LAYER DURING THE DAYTIME
HOURS. THIS WILL KEEP TEMPS QUITE MILD OVERNIGHT WITH MOST AREAS
REMAIN WITHIN A FEW DEGREES EITHER SIDE OF 70.

JOHNSON

LONG TERM...
850 MB THERMAL RIDGE WEAKENS SLIGHTLY AS IT PUSHES BACK WEST THIS
WEEKEND. STILL...TEMPERATURES WILL BE REACHING INTO THE UPPER 90
TO AROUND 100 DEGREES. AN UPPER SHORTWAVE WILL BE MOVING ACROSS
THE PLAINS SATURDAY...WHICH MAY WEAKEN THE CAP ENOUGH FOR ISOLATED
THUNDERSTORMS IN THE AFTERNOON AND EVENING HOURS. WITH CAPES OF
1500 TO 2300 J/KG AND DRY AIR UNDER THE BASE OF STORMS... COULD
SEE A COUPLE SEVERE THUNDERSTORMS. THREATS ARE LARGE HAIL AND
DAMAGING WINDS. WEST CENTRAL TEXAS WILL BE ON THE DRY AND
SUBSIDENT WEST SIDE OF THE UPPER TROUGH ON SUNDAY... WITH HIGHS
AROUND 100 DEGREES.

CONTINUED WARM INTO NEXT WEEK. A WEAK COLD FRONT TUESDAY MAY
PRODUCE ISOLATED THUNDERSTORMS. I LIMITED POPS TO CLIMATOLOGICALLY
FAVORABLE EASTERN SECTIONS. NOT A LOT OF CONFIDENCE IN STORM
DEVELOPMENT HOWEVER WITH UPPER DYNAMICS WELL NORTH OF THE REGION.

04

FIRE WEATHER...
THE DRYLINE WILL MOVE EAST TODAY...SETTLING NEAR A BROWNWOOD TO
JUNCTION LINE THIS AFTERNOON. WEST OF THE DRYLINE...VERY HOT
TEMPERATURES /100-105 DEGREES/ WILL RESULT IN RELATIVE HUMIDITIES
OF 10-20 PERCENT BUT SOUTHWEST 20 FOOT WINDS WILL GENERALLY
REMAIN IN THE 10-12 MPH RANGE...LIMITING FIRE WEATHER CONCERNS
SOMEWHAT. RELATIVE HUMIDITIES ARE FORECAST TO RECOVER TO 70-80
PERCENT BY SATURDAY MORNING...HOWEVER. SOUTH TO SOUTHWEST 20 FOOT
WINDS WILL INCREASE TO 12-16 MPH OVER THE WEEKEND. SLIGHTLY COOLER
TEMPERATURES WILL YIELD RELATIVE HUMIDITIES VALUES OF 20-30
PERCENT SATURDAY AFTERNOON BUT A SHARPER DRYLINE WILL ALLOW
HUMIDITIES TO FALL TO NEAR 10 PERCENT ACROSS THE WESTERN BIG
COUNTRY...CONCHO VALLEY AND CROCKETT COUNTY SUNDAY AFTERNOON. THIS
WILL RESULT IN MARGINALLY ELEVATED FIRE WEATHER CONDITIONS SUNDAY
AFTERNOON.

ELEVATED CONDITIONS ARE EXPECTED AGAIN MONDAY AS SOUTH 20 FOOT
WINDS INCREASE TO 15-18 MPH IN CONJUNCTION WITH RELATIVE
HUMIDITIES NEAR 20 PERCENT. ERC VALUES HAVE DROPPED CLOSER TO
AVERAGE LEVELS OVER THE PAST TWO WEEKS BUT THESE ABNORMALLY HOT
CONDITIONS MAY OFFSET SOME OF THE GREEN-UP AND MOISTURE WITHIN THE
FINER FUELS.

JOHNSON

CLIMATE...
RECORD HIGH TEMPERATURES ARE EXPECTED TODAY AT BOTH ABILENE AND
SAN ANGELO. WE ARE EXPECTING TO SMASH THE SAN ANGELO RECORD OF
100 DEGREES...SET BACK IN 2001. THE FORECAST HIGH IS 106 DEGREES.
AT ABILENE...IT WILL BE MUCH CLOSER. WE ARE CALLING FOR A MAX TEMP
OF 102 DEGREES WHICH WOULD JUST BARELY ECLIPSE THE PREVIOUS MARK
OF 101 DEGREES...SET IN 1978.

WE ARE ALSO LOOKING AT THE POTENTIAL TO SET RECORD HIGH MINIMUM
TEMPERATURES THE NEXT FEW MORNINGS. RECORD HIGH MINS ARE
GENERALLY IN THE LOWER 70S WITH THE FORECAST CALLING FOR LOWS
BETWEEN 71 AND 73 DEGREES AT BOTH ABILENE AND SAN ANGELO.

JOHNSON

&&

.PRELIMINARY POINT TEMPS/POPS...
ABILENE 102  72  97  71  97 /   5   5  20  20   5
SAN ANGELO 106  73 100  72 102 /   5   5  20  20   5
JUNCTION 103  72  98  71 100 /  10  10  20  20  10

&&

.SJT WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

25