Welcome to Today In Weather History for Sunday, January 27, 2008.ġ772 - The "Washington and Jefferson Snowstorm" occurred. THE MID SOUTH AND GULF COAST REGIONS MAY SUPPORT A PERSISTENT SEVERE VALLEY AS FRONT APPROACHES AFTER DARK.GREATER INSTABILITY ACROSS WHILE SEVERE THREAT SHOULD DIMINISH SOMEWHAT INTO THE UPPER OH NWD ACROSS THE TN VALLEY AND PERHAPS INTO THE OH VALLEY. WITH THE POTENTIAL SPREAD ACROSS A BROAD ZONE FROM THE GULF COAST THEREFORE.TORNADOES ARE ALSO ANTICIPATED. THE LARGER CONVECTIVE LINE AS WELL AS WITH ANY STRONGER CELLS AHEAD RESULT IN LOW-LEVEL ROTATION - BOTH WITHIN SMALL-SCALE BOWS ALONG THREAT.LOW-LEVEL WINDS VEERING/INCREASING WITH HEIGHT WILL LIKELY WHILE STRONG/DAMAGING WINDS ARE EXPECTED TO BE THE MAIN SEVERE THROUGH THE AFTERNOON AND INTO THE EVENING. SQUALL LINE TO DEVELOP ALONG THIS FRONT.AND THEN CONTINUE EWD WHILE STORMS AREįORECAST WITHIN BROAD ZONE OF WARM ADVECTION WELL AHEAD OF THEįRONT.GREATEST SEVERE POTENTIAL IS FORECAST CLOSER TO THE MAINTAINS A MOIST BOUNDARY LAYER /SURFACE DEWPOINTS APPROACHING 60ĪS FAR N AS THE LOWER AND MIDDLE OH RIVER VALLEY/. START OF THE PERIOD.WHILE SLY FLOW ACROSS THE WARM SECTOR STORMS SHOULD BE ONGOING ACROSS WRN PORTIONS OF THIS AREA AT THE POTENTIAL FOR TORNADOES - IS ANTICIPATED ACROSS A LARGE PART OF WIDESPREAD SEVERE WEATHER EVENT - INCLUDING DAMAGING WINDS AND THE LA/AR/SERN MO/OH VALLEY EWD TO THE APPALACHIANS. INTO THE ATLANTIC COAST STATES BY 06/12Z. MEANWHILE.THE TRAILING COLD FRONT WILL PROGRESS EWDĪCROSS THE ERN HALF OF THE CONUS.CROSSING THE APPALACHIANS AND LATE AFTERNOON AND THEN NEWD INTO ERN CANADA BY THE END OF THE NEWD ALONG THE SURFACE COLD FRONT.INTO THE OH VALLEY REGION BY IN EXCESS OF 100 KT IN THE JET CORE AND AS HIGH AS 90 KT ATOP THEĪT THE SURFACE.LOW INITIALLY FORECAST INVOF ERN OK SHOULD MOVE WINDS.INCLUDING A SSWLY H8 JET IN EXCESS OF 70 KT AND H5 FLOW WELL SYSTEM WILL BE ACCOMPANIED BY VERY STRONG DEEP-LAYER THEN ACROSS THE GREAT LAKES AND TN/OH VALLEYS THROUGH 06/12Z. LARGE/POSITIVELY-TILTED UPPER TROUGH WILL PROGRESS STEADILY EWDĪCROSS THE CENTRAL U.S. THERE IS A SLGT RISK OF SVR TSTMS FROM LA/AR/SERN MO EWD TO THEĪPPALACHIANS AND NWD INTO THE OH VALLEY. We'll definitely be chasing this event, and will keep you updated as more model runs become available! The dryline storms will also move rapidly eastward into the higher low-level shear as the day progresses, anyway, so either target seems logical from a storm chasing perspectiveĪ moderate risk was issued last night by the Storm Prediction Center in their Day 2 Outlook over the southern MS River Valley and eastward, but this area will definitely be shifted significantly west in the next outlook - probably including most of AR and maybe even Eastern OK and Northeast TX. The eastern supercells will likely have the highest potential of producing long-track strong tornadoes given the very high 0-1 km helicity values, but tornadoes cannot be ruled out along the dryline as well. A likely scenario for tomorrow's severe weather event is the development of two bands of supercells: one over Arkansas and northern Louisiana along a pre-frontal confluence line early in the afternoon, and a second along the dryline further west across eastern Oklahoma and extreme Northeast Texas. However, this area still has little or no capping inversion despite lesser CAPE, and is still supportive of strong tornadoes. Selected WRF forecast panels for 00z tomorrow are displayed below.Īs is commonly the case with this type of event, the core of the LLJ and the best low-level shear will be slightly east of the dryline and the best instability, as can be seen in the CAPE and 850 mb forecasts above. Given 0-1 km helicity values of 200+ m2/s2 over the entire warm sector, these tornadoes could be strong and long-track (especially with the fast storm motions).
Beginning early tomorrow afternoon, or even late tonight, the threat for tornadoes will increase dramatically over Northeast TX, East OK, and AR as supercells become surface-based. Therefore, the severe weather threat for today will hold off until after dark when the upper-level support arrives. The models have been trending slower and slower with this system with each consecutive run, with the WRF now forecasting the dryline to cross the I-35 corridor late tomorrow (Tuesday) morning. A severe weather outbreak is likely tonight through tomorrow from the eastern Southern Plains east to the Mississippi River Valley (Southern IL southward).
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