Area Forecast Discussion
Issued by NWS Hastings, NE

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000
FXUS63 KGID 221741
AFDGID

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
1241 PM CDT TUE JUL 22 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 501 AM CDT TUE JUL 22 2014

IN SHORT...THERE ARE TWO MAIN CONCERNS THROUGH THE NEXT 24
HOURS...ONE BEING ANOTHER DAY OF AT LEAST MARGINALLY-ADVISORY
LEVEL HEAT INDEX VALUES ACROSS ROUGHLY THE SOUTHEAST 1/2 OF THE
CWA...AND THE OTHER BEING WHETHER OR NOT A FEW ISOLATED
STORM/POSSIBLY A BROKEN LINE OF STORMS CAN FLARE UP AND BECOME
STRONG TO SEVERE GENERALLY NEAR/SOUTH OF THE STATE LINE LATE THIS
AFTERNOON INTO THIS EVENING ALONG A SURFACE COLD FRONT. BOTH
BEFORE AND AFTER THIS MAIN TIME FRAME OF CONCERN FOR POSSIBLE
STRONG CONVECTION...AT LEAST ISOLATED CONVECTION CANNOT BE
COMPLETELY RULED OUT. STARTING WITH THIS MORNING...SUPPOSE A FEW
ROGUE SHOWERS/POSSIBLY A WEAK ELEVATED STORM SLIPPING INTO MAINLY
NORTHERN PORTIONS OF THE CWA IS NOT OUT OF THE QUESTION...BUT
CONFIDENCE IN THIS OCCURRING IS NOT HIGH ENOUGH TO INTRODUCE A
FORMAL MENTION INTO A PREVIOUSLY-DRY FORECAST. THEN LATE
TONIGHT...GENERALLY AFTER MIDNIGHT...CONFIDENCE IS VERY LOW ON
WHAT WILL TRANSPIRE...AS SOME MODELS SHOW POTENTIALLY WIDESPREAD
CONVECTION DEVELOPING OVER OR MOVING INTO PRIMARILY THE SOUTHWEST
1/2 OF THE CWA...WHILE OTHERS ARE BONE DRY.

STARTING WITH THE HERE AND NOW AS OF 09Z/4 AM...DRY CONDITIONS ARE
IN PLACE OVER THE CWA...WHILE AT LEAST A FEW COUNTIES OUTSIDE THE
LOCAL AREA A SMATTERING OF WEAK ELEVATED THUNDERSTORMS ARE
ROAMING PARTS OF WESTERN/NORTH CENTRAL NEB AND ALSO A SMALL
PORTION OF WEST CENTRAL IA. THE ACTIVITY TO THE NORTH AND WEST
APPEARS TO BE TIED MAINLY TO AN EAST-WEST ORIENTED ZONE OF
FRONTOGENESIS IN THE 850-700MB LAYER. IN THE BIGGER
PICTURE...WATER VAPOR SATELLITE IMAGERY ALONG WITH SHORT TERM
MODEL DATA HIGHLIGHT THE EXPANSIVE HIGH/ANTICYCLONE EXTENDING
EASTWARD INTO THE CENTRAL PLAINS FROM ITS CENTRAL CORE OVER THE
NM/CO BORDER AREA. IN THE STRONGER FLOW TO THE THE NORTH...A
VIGOROUS SHORTWAVE TROUGH WAS TRACKING EASTWARD ACROSS NORTHERN
MN. ESSENTIALLY...THE LOCAL AREA LIES ALONG THE INTERFACE BETWEEN
VERY WEAK MID/UPPER FLOW TO THE SOUTH AND SOMEWHAT STRONGER
WESTERLY FLOW JUST TO THE NORTH ALONG THE FRINGES OF THE RIDGE
AXIS. AT THE SURFACE...HIGH PRESSURE CENTERED OFF TO THE NORTH IN
THE WAKE OF THE NORTHERN MN SHORTWAVE TROUGH HAS PUSHED A MODEST
COLD FRONT SOUTHWARD INTO NEBRASKA OVERNIGHT...WITH ITS LEADING
EDGE ALREADY WORKING INTO NORTHERN PORTIONS OF THE CWA AS
EVIDENCED BY A SHIFT TO SOME NORTHERLY WIND COMPONENT...WHILE THE
MAJORITY OF THE CWA HAS OBSERVED SOME VARIATION OF SOUTHERLY TO
WESTERLY BREEZES IN THE 5-15 MPH RANGE OVERNIGHT. ALTHOUGH SOME
DRIER LOW- 60S DEWPOINTS HAVE ADVECTED INTO WESTERN ZONES
OVERNIGHT...MUCH OF THE EASTERN CWA CONTINUES HOLDING ONTO UPPER
60S-LOW 70S DEWPOINTS...MAKING FOR ANOTHER SEASONABLY WARM
MORNING. LOW TEMPS WILL LIKELY EXHIBIT A RANGE FROM UPPER
60S/NEAR-70 WEST TO UPPER 70S-NEAR 80 EAST GIVEN THIS DEWPOINT
GRADIENT.

HEADING INTO THE DAYTIME HOURS...THE BIG PICTURE ALOFT INVOLVES A
TRANSITION FROM MORE WESTERLY TO MORE NORTHERLY MID-UPPER LEVEL
FLOW...IN RESPONSE TO THE EXPANSIVE RIDGE EDGING SLIGHTLY NORTH
MORE OVER CO...AND THE NORTHEAST EDGE OF THIS RIDGE AXIS CLOSER TO
THE LOCAL AREA BEING FLATTENED SOMEWHAT IN THE WAKE OF THE
DEPARTING GREAT LAKES AREA TROUGH. MEANWHILE AT THE SURFACE...THE
COLD FRONT WILL CONTINUE SINKING SOUTHWARD ACROSS THE AREA AS HIGH
PRESSURE SHIFTS EASTWARD ACROSS THE DAKOTAS/MN AREA. ALTHOUGH THE
SOUTHWARD PUSH OF THIS FRONT SHOULD EASE WITH TIME...MOST OF SOUTH
CENTRAL NEBRASKA SHOULD OBSERVE PREVAILING NORTHEAST BREEZES UP TO
AROUND 10-15 MPH THROUGH MOST OF THE DAY...WHILE LOCATIONS NEAR
THE STALLING SOUTHERN EDGE OF THIS BOUNDARY NEAR AND SOUTH OF THE
STATE LINE WILL OBSERVE A LIGHT/VARIABLE TO LIGHT SOUTHERLY BREEZE
AS THE FRONT IS REINFORCED NEAR THE STATE LINE IN RESPONSE TO WEAK
LOW PRESSURE CENTERED NEAR THE CO/KS BORDER. ALTHOUGH VERY WARM
MID LEVEL TEMPS ON THE ORDER OF 13-15C AT 700MB SHOULD CONTINUE TO
FIRMLY CAP LOW-LEVEL BASED CONVECTION THROUGH AT LEAST THE
MAJORITY OF THE DAY...THERE ARE HINTS THAT A FEW ELEVATED
SPRINKLES OR EVEN WEAK STORMS COULD PERCOLATE ABOVE THE CAP ALONG
THE ELEVATED FRONTAL ZONE MAINLY THIS MORNING...AND WILL HAVE TO
KEEP AN EYE OUT IN CASE SOME LOW POPS MIGHT NEED ADDED TO MAINLY
THE NORTHERN CWA. OTHERWISE...THE MAIN FOCUS FOR POTENTIALLY MORE
NOTEWORTHY AND LOWER-BASED CONVECTION SHOULD HOLD OFF UNTIL LATE
AFTERNOON/EARLY EVENING NEARER THE SURFACE FRONT NEAR THE STATE
LINE. ALTHOUGH THIS DEVELOPMENT IS CERTAINLY NO GUARANTEE GIVEN
THE STRONG CAP...THE HOT/DEEPLY MIXED AIRMASS SOUTH OF THE FRONT
MAY BE ENOUGH TO TRIGGER AT LEAST ISOLATED CONVECTION IN AN
ENVIRONMENT CHARACTERIZED BY AROUND 2000-3000 J/KG MIXED LAYER
CAPE BUT ONLY AROUND 25KT AT MOST OF DEEP LAYER SHEAR. SOME MODELS
ARE MORE AGGRESSIVE WITH OTHERS IN THIS STORM DEVELOPMENT...AS FOR
EXAMPLE THE 00Z 4KM NSSL WRF STRONGLY SUGGESTS IT WHILE THE LATEST
08Z RAP KEEPS STORMS AT BY LOCALLY THROUGH AT LEAST 02Z/9PM. AT
ANY RATE...MAINTAINED THE SLIGHT POPS FOR LATE THIS AFTERNOON/THIS
EVENING TO COVER AT LEAST THE POSSIBILITY OF THIS DEVELOPMENT
ALONG THE EAST-WEST FRONTAL ZONE. DESPITE THE VERY CONDITIONAL
NATURE OF THIS STORM DEVELOPMENT...THE STORM PREDICTION CENTER
UPGRADED MUCH OF THE SOUTHERN CWA TO A SLIGHT RISK ON THE DAY 1
OUTLOOK...WITH THE MAIN THREATS LIKELY BEING STRONG OUTFLOW
WINDS/DOWNBURST ACTIVITY...AND LESS-SO LARGE HAIL GIVEN SUCH WARM
THERMAL PROFILES. SPEAKING OF THERMAL...TEMPERATURES AND DEWPOINTS
HAVE BEEN A BIT OF A CHALLENGE FOR TODAY...AS MUCH OF THIS DEPENDS
ON HOW FAST THE SLIGHTLY COOLER AIR CAN FILTER IN FROM THE NORTH
TODAY...AND WHETHER DEWPOINTS AGAIN SPIKE BACK UP BEHIND THIS
BOUNDARY AFTER FALLING OFF SOMEWHAT OVERNIGHT. TOOK A BEST STAB AT
HIGHS USING A BLEND OF VARIOUS MODELS...YIELDING A RANGE FROM LOW
90S FAR NORTH...MID 90S CENTRAL AND GENERALLY 100-102 IN KS ZONES.
WOULD NOT BE SURPRISED THOUGH TO SEE PARTS OF THE NORTH STAY A FEW
DEGREES COOLER AND PARTS OF THE SOUTH RISE A FEW DEGREES HIGHER.
THE NET RESULT FOR HEAT INDEX VALUES IS THAT AREAS MAINLY SOUTH OF
A YORK-MINDEN LINE (INCLUDING KS) APPEAR MOST FAVORED TO
REACH/SLIGHTLY EXCEED 105...AND THUS HAVE GONE WITH AN ADVISORY
FOR THESE LOCATIONS ALTHOUGH DO NOT EXPECT AS MUCH OF THE HIGHER-
THAN-EXPECTED COVERAGE OF 110+ HEAT INDEX READINGS THAT
MATERIALIZED YESTERDAY IN EASTERN ZONES. OUTSIDE THE ADVISORY AREA
TO THE NORTH AND WEST...IT WILL OBVIOUSLY STILL BE HOT...BUT
LOOKING FOR SUB-ADVISORY LEVEL HEAT INDEX VALUES MORE INTO THE
95-102 RANGE.

FOR THIS EVENING/TONIGHT...OBVIOUSLY HEAT INDEX/ADVISORY ISSUES
WILL QUICKLY ABATE...LEAVING THE ULTIMATE QUESTION AS TO HOW MUCH
IF ANY CONVECTION AND POSSIBLE STRONG-SEVERE STORM POTENTIAL
REMAINS THROUGH THE NIGHT. AS FOR THE BIG PICTURE OF THE MID-UPPER
LEVELS...FLOW WILL TURN EVEN MORE NORTHERLY AS THE STRONG HIGH
PRESSURE CENTER PARKS ITSELF FIRMLY OVER CENTRAL CO...WHICH ACTUALLY
ALLOWS MID LEVEL TEMPS TO COOL VERY SLIGHTLY OVER THE LOCAL AREA
AS A LOW-AMPLITUDE SHORTWAVE TROUGH BRUSHES BY ALONG A TRACK FROM
THE DAKOTAS INTO IA OVERNIGHT. AT THE SURFACE...GENERALLY EAST-
NORTHEAST BREEZES AROUND 10 MPH WILL PREVAIL OVERNIGHT AS HIGH
PRESSURE REMAINS CENTERED WELL OFF TO THE NORTHEAST OF THE LOCAL
AREA. AS MENTIONED ABOVE...THERE IS TREMENDOUS UNCERTAINTY IN THE
CONVECTIVE POTENTIAL OVERNIGHT. ONE SCENARIO IS THAT ONCE ANY
EVENING ACTIVITY DIES OUT OR MOVES OUT OF THE AREA IN THE SOUTHERN
CWA ALONG THE FRONTAL ZONE THAT NOTHING ELSE OCCURS THE REST OF
THE NIGHT (PER THE ECMWF AND ALSO THE NSSL 4KM-WRF).
MEANWHILE...OTHER MODELS SUCH AS THE NAM/GFS AND ALSO THE 4KM
WRF-NMM SIMULATED REFLECTIVITY SHOW POTENTIALLY A FAIR AMOUNT OF
CONVECTION AFFECTING MAINLY THE SOUTHWEST HALF OF THE CWA AFTER
MIDNIGHT...POSSIBLY AS A RESULT OF A STORM COMPLEX RIDING
SOUTHEASTWARD INTO THE AREA OUT OF THE BLACK HILLS/NORTHWEST NEB
AREA. GIVEN THE TREMENDOUS UNCERTAINTY HERE...OPTED NOT TO GET
CUTE WITH THE FORECAST AND JUST BLANKETED MUCH OF THE
CENTRAL/SOUTHERN CWA WITH A GENERIC SLIGHT 20 PERCENT POP FOR THE
LATER NIGHT HOURS. BESIDES CONVECTIVE POTENTIAL...SUPPOSE AT LEAST
SOME LIGHT FOG CANNOT BE RULED OUT LATE TONIGHT MAINLY IN WESTERN
ZONES...BUT CURRENT MODELS/GUIDANCE DO NOT SUPPORT VISIBILITY
RESTRICTIONS BAD ENOUGH/WIDESPREAD ENOUGH FOR A FORMAL FORECAST
INCLUSION AT THIS TIME. AS FOR LOW TEMPS...ONLY MADE MINOR TWEAKS
AIMING FOR A RANGE FROM MID 60S NORTH TO AROUND 70 SOUTH.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 501 AM CDT TUE JUL 22 2014

TEMPS WILL BE UP AND DOWN DURING THE EXTENDED PERIODS AND ALTHOUGH
THERE ARE HIT OR MISS CHCS FOR TSTMS...NOTHING IS LOOKING WIDESPREAD
OR SIGNIFICANT AT THIS POINT IN TIME.

FOLLOWING THE REALLY HOT TEMPERATURES MONDAY AND TUESDAY...READINGS
WILL TREND COOLER ON WEDNESDAY AS THE UPPER RIDGE AXIS RETROGRADES
ALONG THE HIGH PLAINS AND A TROUGH DEEPENS FM THE GREAT LAKES THRU
THE OHIO VALLEY REGION.  THE HOT AIR RETREATS AND COOLER AIR BACKS
IN FROM THE EAST AND H85 TEMPS COOL SEVERAL DEGREES AND WE ARE
LOOKING FOR AFTERNOON HIGHS TO RANGE FROM THE MID 80S IN OUR EASTERN
ZONES TO AROUND 90F IN THE SW. A 1020MB SFC HIGH PRESSURE SYSTEM
BUILDS SOUTH FROM THE UPPER MIDWEST WHICH WILL RESULT IN EASTERLY
LLVL FLOW AND BRING THE COOLEST CONDITIONS TO OUR EASTERN ZONES.
HAVE KEPT THE FORECAST DRY BUT THERE IS AN OUTSIDE CHC FOR REMNANT
CONVECTION TO LINGER FOR A TIME WEDNESDAY MORNING IN THE VCNTY OF
THE FRONTAL BOUNDARY IN OUR SOUTH.

TEMPERATURES WILL BE ON THE INCREASE AGAIN THURSDAY FRIDAY AS THE
UPPER RIDGE AXIS BUILDS EAST AGAIN AHEAD OF AN UPPER LOW TRANSLATING
EAST FROM THE PACIFIC NORTHWEST. THE RIDGE AXIS DEAMPLIFIES BY THE
END OF THE WEEK BUT THE AIRMASS REMAINS QUITE WARM THRU FRIDAY AND
HIGH TEMPERATURES SHOULD AGAIN AVERAGE IN THE 90S.  A PROGRESSING
MID LEVEL SHORTWAVE TROUGH AND WAA AHEAD OF THE SYSTEM WILL BRING
THE POTENTIAL FOR TSTMS THURSDAY AND THURSDAY NIGHT.  THEN...A COLD
FRONT ASSOCIATED WITH THE NORTHERN CONUS SYSTEM PUSHES SOUTHEAST
DURING THE DAY ON FRIDAY BUT CHCS FOR STORMS LOOK NEGLIGIBLE WITH
THE BOUNDARY.

OVER THE WEEKEND AND EARLY NEXT WEEK THE UPPER RIDGE RETROGRADES AND
BUILDS OVER THE ROCKIES WHILE AN UPPER TROUGH DEEPENS FM THE GREAT
LAKES THROUGH THE OHIO VALLEY. COOLER AIR WILL RETURN IN THE MORE
MERIDIONAL FLOW AND TEMPERATURES WILL DROP BACK CLOSER TO SEASONAL
READINGS OR BELOW.  CANNOT COMPLETELY RULE OUT PCPN CHCS IN THE
OUTER PERIODS AS TEMPERATURES COOL ALOFT AND BOUNDARIES MOVE THRU.
THIS BEING SAID NOTHING SAID THERE IS NO REAL CONCLUSIVE PERIOD FOR
CONVECTION EITHER AND HAVE ONLY CARRIED LOW POPS IN OUR SOUTH FOR
SUNDAY NIGHT.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1232 PM CDT TUE JUL 22 2014

VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD. WINDS SHOULD BE
EAST TO NORTHEAST.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...HEAT ADVISORY UNTIL 8 PM CDT THIS EVENING FOR NEZ064-074>077-
     083>087.

KS...HEAT ADVISORY UNTIL 8 PM CDT THIS EVENING FOR KSZ005>007-017>019.

&&

$$

SHORT TERM...PFANNKUCH
LONG TERM...FAY
AVIATION...JCB



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