All Weather News

SPC Issues Moderate Risk Today

10 Feb 2009, 10:17 am
Convective Outlook
Convective Outlook
Tornado Probabilities
Tornado Probabilities

Damaging Wind Probabilities
Damaging Wind Probabilities

The Storm Prediction Center has issued a moderate risk in their convective outlook category for severe thunderstorm development today for eastern Texas, southeastern Oklahoma, western Arkansas, and northwestern Louisiana.

Convective initiation should occur in the early afternoon between southeastern Oklahoma and northeastern Texas as warm air advection meets with an ejecting mid-level jet maxima, however the best opportunity for surface based initiation will be slightly west of the initial development along a developing dryline near the I-35 corridor. Keep an eye on our SuperSats and Radar Center for developments.

The SPC has also released enhanced Tornado Probabilities for today’s storms including their “hatched area” defined as a region with a greater than 10% probability of an EF2-EF5 tornado forming within 25 miles of their outlined area of interest.

This is due to the forecast vertical shear profiles of greater than 300 meters per second 0-1km srh and 60 knot bulk shear which when combined with ~ 1500 j/kg CAPE favors at least with the initial convective initiation the probability of discrete supercells. This with strong low-level shear and abundant moisture at lower levels supports the possibility of sustained supercells after development that can equate to long-track tornadoes.

As the evening wears on a cold front will overtake the initial dryline causing the formation of a squall line. Low level shear will remain quite favorable with this development where tornadoes are still possible that can occur within embedded circulations within the line, perhaps a few bookend vortices.

However, as is often the case strong damaging winds are the main threat with the squall line, which is why they SPC issued their enhanced Damaging Wind Probabilities area covering a range just beyond that of the moderate risk.

Depending upon later model runs, if the shear profiles and thermal probabilities hold true, it is possible they may upgrade their Convective Outlook to a high risk category. However, the opposite is of course true as well.

For grins and giggles I have also run our Forecast Precipitation Type Radar that shows the projected convective initiation mentioned above. Compare it to the actual development in our Radar Center to see how closely it holds true!

Recall that the Forecast Radar shows where over a three hour interval ending at that three hour interval (remember the time difference, currently -5 for eastern) precipitation is forecast to occur. Our forecast product also shows the liquid precipitation streaming through the northeastern states by Thursday, and new snows entering the central plains on Friday that we will discuss later.

Please be sure to view our Advisory and Radar Centers for the latest updates and developments.

As always stay tuned to your favorite weather outlet, stay informed, and stay safe!

Public Severe Weather Outlook Issued by the SPC
ZCZC SPCPWOSPC ALL
WOUS40 KWNS 101102
ARZ000-LAZ000-OKZ000-TXZ000-101900-

PUBLIC SEVERE WEATHER OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0502 AM CST TUE FEB 10 2009

…SEVERE WEATHER OUTBREAK EXPECTED OVER THE ARKLATEX LATER THIS
AFTERNOON AND TONIGHT…

THE NWS STORM PREDICTION CENTER IN NORMAN OK IS FORECASTING THE
DEVELOPMENT OF A FEW STRONG…LONG-TRACK TORNADOES AND WIDESPREAD
DAMAGING WINDS OVER PARTS OF THE ARKLATEX LATER THIS AFTERNOON AND
TONIGHT.

THE AREAS MOST LIKELY TO EXPERIENCE THIS ACTIVITY INCLUDE

WESTERN AND CENTRAL ARKANSAS
NORTHWEST LOUISIANA
EASTERN OKLAHOMA
NORTH-CENTRAL AND NORTHEAST TEXAS

ELSEWHERE…SEVERE STORMS ARE ALSO POSSIBLE FROM THE MID MISSISSIPPI
VALLEY INTO CENTRAL AND SOUTHEAST TEXAS.

A POWERFUL WINTER STORM SYSTEM OVER THE LOWER COLORADO VALLEY THIS
MORNING WILL MOVE EAST THROUGH THE SOUTHERN ROCKIES INTO THE
SOUTHERN PLAINS BY TONIGHT. LOW-LEVEL MOISTURE WILL CONTINUE TO
INCREASE TODAY OVER LOWER ELEVATIONS OF THE SOUTHERN PLAINS INTO
LOWER MISSISSIPPI VALLEY AS SOUTHERLY WINDS STRENGTHEN IN ADVANCE OF
THE UPPER-LEVEL STORM SYSTEM. THIS MOISTURE WILL COMBINE WITH
DAYTIME HEATING AND COOLING TEMPERATURES ALOFT TO CREATE A
MODERATELY UNSTABLE AIR MASS BY AFTERNOON GENERALLY ALONG AND EAST
OF THE I-35 CORRIDOR OF OKLAHOMA AND TEXAS.

RAPID THUNDERSTORM DEVELOPMENT IS EXPECTED BY MID TO LATE AFTERNOON
ALONG A DRYLINE FROM NEAR OR SOUTH OF OKLAHOMA CITY SOUTHWARD TO THE
DALLAS-FORT WORTH METROPLEX AS THE APPROACHING UPPER-LEVEL SYSTEM
BEGINS TO EXERT AN INFLUENCE ON THE DESTABILIZING AIR MASS. THE
COMBINATION OF STRONG VERTICAL SHEAR AND A MODERATELY UNSTABLE AND
EXPANDING WARM SECTOR SUGGESTS THE LIKELIHOOD OF A FEW SUPERCELLS
CAPABLE OF PRODUCING STRONG…POTENTIALLY LONG-TRACKED TORNADOES.
THIS TORNADO THREAT APPEARS TO BE GREATEST OVER SOUTHEAST
OKLAHOMA…NORTHEAST TEXAS…WEST-CENTRAL AND SOUTHWEST ARKANSAS
INTO NORTHWEST LOUISIANA LATE THIS AFTERNOON INTO TONIGHT.

ADDITIONAL STORMS…LIKELY IN THE FORM OF A SQUALL LINE…ARE
EXPECTED TO DEVELOP OVER PARTS OF EASTERN OKLAHOMA INTO EASTERN
TEXAS TONIGHT AS A FAST-MOVING PACIFIC FRONT OVERTAKES THE DRYLINE.
WHILE A FEW TORNADOES AND SOME HAIL WILL BE POSSIBLE WITH THESE
STORMS…IT APPEARS THAT DAMAGING WINDS WILL BE THE PRIMARY SEVERE
WEATHER HAZARD. THIS DAMAGING WIND THREAT WILL LIKELY CONTINUE
EASTWARD INTO PARTS OF ARKANSAS AND LOUISIANA OVERNIGHT.

THIS IS POTENTIALLY A VERY DANGEROUS SITUATION. THOSE IN THE
THREATENED AREA ARE URGED TO REVIEW SEVERE WEATHER SAFETY RULES AND
TO LISTEN TO RADIO…TELEVISION…AND NOAA WEATHER RADIO FOR
POSSIBLE WATCHES…WARNINGS…AND STATEMENTS LATER TODAY.

..MEAD.. 02/10/2009

$$

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