Storm Prediction Center Forecast
No watches are valid as of Sat Sep 4 12:30:02 UTC 2010.
No Mesoscale Discussions are in effect as of Sat Sep 4 12:30:02 UTC 2010.
SPC 1300Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0721 AM CDT SAT SEP 04 2010
VALID 041300Z - 051200Z
...NO SVR TSTM AREAS FORECAST...
...NRN INTERMOUNTAIN REGION INTO NRN HIGH PLAINS...
LARGE-SCALE TROUGH CENTERED OVER BRITISH COLUMBIA EARLY THIS MORNING
WILL SHIFT EWD THROUGH THE PERIOD IN RESPONSE TO APPROACH OF NEXT
UPSTREAM SYSTEM THROUGH THE GULF OF AK. AS THIS OCCURS...AN
UPSTREAM VORTICITY MAXIMUM AND ATTENDANT MID TO UPPER-LEVEL STREAKS
ALONG THE BRITISH COLUMBIA COAST WILL PROPAGATE SEWD...CONTRIBUTING
TO A NET SEWD DEVELOPMENT/AMPLIFICATION OF BROADER-SCALE TROUGH
THROUGH THE PACIFIC NW AND NRN INTERMOUNTAIN REGION. AT THE
SURFACE...AN ASSOCIATED COLD FRONT WILL PROGRESS EWD ACROSS THE
REGION...SERVING AS THE FOCUS FOR STRONG TO MARGINALLY SEVERE STORMS
THIS AFTERNOON THROUGH EVENING.
SATELLITE-DERIVED PW IMAGERY SHOWS A SLIGHT INCREASE IN MOISTURE
FROM THE ERN PACIFIC THIS MORNING...THOUGH IN GENERAL...AIR MASS
WILL REMAIN RATHER DRY WITH DEW POINTS IN THE 40S AND PW VALUES LESS
THAN AN INCH. HOWEVER...REGION WILL RESIDE WITHIN A PLUME OF STEEP
MIDLEVEL LAPSE RATES...WHICH WHEN COUPLED WITH DAYTIME
HEATING...SHOULD YIELD AFTERNOON MLCAPE OF 250-500 J/KG. THIS
DESTABILIZATION COMBINED WITH INCREASED HEIGHT FALLS/DYNAMIC FORCING
FOR ASCENT IN ADVANCE OF MIDLEVEL TROUGH SHOULD FOSTER SCATTERED
STORM FORMATION ALONG THE FRONT THIS AFTERNOON OVER WRN AND CNTRL
MT. AMBIENT INFLOW AIR MASS WILL BE CHARACTERIZED BY A DEEPLY-MIXED
PBL WITH 40-50 KT OF WLY DEEP-LAYER SHEAR WHICH WILL BE SUPPORTIVE
OF HIGH-BASED STORMS /INCLUDING POSSIBLE SUPERCELLS/ WITH THE THREAT
FOR ISOLATED STRONG WIND GUSTS AND MARGINALLY SEVERE HAIL. TSTMS
SHOULD TEND TO WEAKEN BY MID TO LATE EVENING AS THE BOUNDARY LAYER
COOLS AND SURFACE-BASED CONVECTIVE INHIBITION RAPIDLY ACCUMULATES.
..MEAD/GRAMS.. 09/04/2010
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Day 4-8 Outlook
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0351 AM CDT SAT SEP 04 2010
VALID 071200Z - 121200Z
...DISCUSSION...
AS GOOD AGREEMENT CONTINUES AMONG LATEST ECMWF/GEFS GUIDANCE...IT IS
LIKELY THAT A RELATIVELY MORE ACTIVE PATTERN WILL DEVELOP ACROSS THE
NORTH CENTRAL STATES DURING THE MIDDLE TO LATTER PART OF NEXT WEEK.
THIS WILL BE IN ASSOCIATION WITH THE EASTWARD ADVANCEMENT OF A
WESTERN STATES UPPER TROUGH...ALONG WITH THE ANTICIPATED
AVAILABILITY OF A BROAD/HIGHER QUALITY MOIST SECTOR GIVEN A
STALLING/RETREATING CENTRAL STATES FRONT DURING THE MIDDLE PART OF
THE WEEK. INITIALLY...IT APPEARS THAT SOME SEVERE RISK MAY EXIST ON
DAY 5/WEDNESDAY ACROSS THE NORTH-CENTRAL HIGH PLAINS. A MORE
APPRECIABLE SEVERE RISK SHOULD UNFOLD INTO DAYS 6/7...MAINLY THE
DAKOTAS AND WESTERN/NORTHERN NEB ON DAY 6/THURSDAY...AND PERHAPS THE
UPPER MS RIVER VALLEY ON DAY 7/FRIDAY. WHILE CURRENT THINKING IS
THAT CATEGORICAL SLIGHT RISKS WILL ULTIMATELY BE WARRANTED IN THIS
TIME FRAME...LARGE SCALE TIMING UNCERTAINTY/INHERENT UNKNOWNS
CURRENTLY PRECLUDE DELINEATION OF ANY HIGHER PROBABILITY /30 PERCENT
AND GREATER/ SEVERE RISK AREAS.
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SPC Day 2 Fire Weather Outlook
DAY 2 FIRE WEATHER OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0458 AM CDT SAT SEP 04 2010
VALID 051200Z - 061200Z
...CRITICAL FIRE WEATHER AREA FOR MOST OF THE ERN GREAT BASIN TO THE
CNTRL ROCKIES...
...SYNOPSIS...
A LARGE-SCALE UPPER-LEVEL TROUGH WILL CONTINUE TO DIG ACROSS THE
NWRN CONUS AND PROGRESS EWD TOWARDS THE NRN/CNTRL ROCKIES THROUGH
EARLY MON. MID-LEVEL WLYS WILL STRENGTHEN WITH A BELT OF 50 TO 70
MPH FLOW AT 500 MB CENTERED ACROSS NRN NV/SRN ID INTO WY ON SUN
AFTERNOON. AT THE SURFACE...A SHARP COLD FRONT WILL SWEEP SWD
THROUGH THE GREAT BASIN...WITH TIGHT THERMAL AND PRESSURE GRADIENTS
DEVELOPING IN ITS WAKE.
...MOST OF THE ERN GREAT BASIN TO THE CNTRL ROCKIES...
WIDESPREAD CRITICAL CONDITIONS APPEAR LIKELY SUN AFTERNOON AHEAD OF
A SHARP COLD FRONT ACROSS NRN AZ...SRN/ERN UT...NRN/WRN CO AND
CNTRL/SRN WY. SUSTAINED SURFACE WINDS WILL INCREASE TO 20 TO 30
MPH...WITH WIND GUSTS LOCALLY REACHING 40 TO 50 MPH OVER PORTIONS OF
SRN WY/NWRN CO. THIS WILL COINCIDE WITH AN ANTECEDENT VERY WARM/DRY
AIR MASS /RH VALUES OF 5 TO 15 PERCENT/.
THE CRITICAL AREA HAS BEEN EXTENDED FARTHER NW INTO NERN NV/NWRN
UT/SERN ID. HERE...STRONG SURFACE WINDS /FROM 20 TO 30 MPH/ DURING
THE AFTERNOON WILL PERSIST INTO THE EVENING AS THE POST-FRONTAL
PRESSURE GRADIENT STRENGTHENS. DESPITE COOLING TEMPERATURES WITH
WINDS VEERING TO THE N/NW...CONSENSUS OF MODEL FORECASTS SUGGESTS RH
RECOVERY WILL INITIALLY BE POOR DURING THE EARLY EVENING AS GUSTS
AOA 30 MPH CONTINUE. ALTHOUGH MIN RH VALUES MAY BE MARGINAL /AROUND
15 PERCENT/...THE STRENGTH AND DURATION OF WINDS WARRANT A CRITICAL
DELINEATION.
...PORTIONS OF THE TX/OK PANHANDLES...SWRN KS...NWRN OK...
MARGINAL TO LOCALIZED CRITICAL CONDITIONS MAY DEVELOP AROUND PEAK
HEATING ON SUN. THE STRONGEST LOW-LEVEL SLYS SHOULD PRIMARILY BE
CONFINED E OF A DRYLINE MIXING ACROSS THE CNTRL/SRN PLAINS...WHERE
RH VALUES WILL BE INCREASINGLY MARGINAL WITH ERN EXTENT.
HOWEVER...AS LEE CYCLOGENESIS ENSUES INVOF NERN CO...A TIGHTENING
SURFACE PRESSURE GRADIENT W OF THE DRYLINE WILL OCCUR ACROSS THE
TX/OX PANHANDLES DURING MID TO LATE AFTERNOON. SUSTAINED SURFACE
WINDS SHOULD REACH 15 TO 20 MPH WITH RH VALUES OF 10 TO 20 PERCENT.
...NRN SACRAMENTO VALLEY IN NRN CA...
A HIGHLY LOCALIZED ENHANCED FIRE WEATHER THREAT SHOULD DEVELOP LATE
SUN AFTERNOON THROUGH THE EVENING. GUSTY NLY WINDS WILL DEVELOP AS
LOW-LEVEL PRESSURE GRADIENTS TIGHTEN SUBSTANTIALLY WITH A RIDGE
BUILDING INTO THE PACIFIC NW. SUSTAINED SURFACE WINDS SHOULD BECOME
MODERATE...REACHING 15 MPH. THIS WOULD BE INITIALLY JUXTAPOSED WITH
LOW RH VALUES OF 6 TO 12 PERCENT...AND POOR RH RECOVERY IS EXPECTED
THROUGH MUCH OF THE NIGHT.
..GRAMS.. 09/04/2010
...PLEASE SEE WWW.SPC.NOAA.GOV/FIRE FOR GRAPHIC PRODUCT...
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