National Weather Outlook
Our slow moving storm system continues to gradually lift northeast through the Upper Midwest through the end of the week. The heaviest precipitation over the next few days will be across the Central and Southern Plains with heavier thunderstorm activity. Note the area of low pressure developing near the Carolina Coast! That low pressure system has some sub-tropical characteristics and has caught the attention of the National Hurricane Center.
The forecast by midday Thursday shows a fairly robust area of low pressure just off the Carolina Coast. Gusty winds and locally heavy rainfall will be associated with the storm system, but widespread stronger rip current potential will be found along the beaches from the Carolinas to Florida.
For the North Atlantic…Caribbean Sea and the Gulf of Mexico:
1. Disorganized showers and thunderstorms extending over portions of Florida, the Bahamas, and adjacent waters are associated with an upper-level trough and a weak surface low located over the northwestern Bahamas. The aircraft reconnaissance mission scheduled for this afternoon has been cancelled. However, conditions are expected to become gradually more favorable for development over the next day or so while the system moves slowly northward. A subtropical or tropical cyclone could form by Thursday or Friday, and interests along the southeast coast of the United States should monitor the progress of this system through the weekend.
The next Special Tropical Weather Outlook will be issued on this system by 8 PM EDT today. For additional information, see High Seas Forecasts issued by the National Weather Service.
* Formation chance through 48 hours…medium…60 percent
* Formation chance through 5 days…medium…60 percent
Lack of Severe Weather in 2015?
According to NOAA’s Storm Prediction Center, the 2015 PRELIMINARY tornado count through May 5th is 238. The 2005-2014 average is 544, so we are nearly 300 below the short-term average! During the specified years, the only other year that had fewer tornado reports than 2015 was in 2013 when there were only 236 reports through May 5th.
Severe Threat Wednesday
…SUMMARY… SEVERE THUNDERSTORMS WILL BE POSSIBLE THURSDAY FROM PORTIONS OF THE MIDWEST SOUTHWESTWARD INTO THE SOUTHERN AND CENTRAL PLAINS. THE GREATEST POTENTIAL WILL EXIST FROM SOUTHWEST KANSAS SOUTHWARD INTO NORTHWEST TEXAS. …SYNOPSIS… AN UPPER LEVEL LOW OVER NRN CA AT 12Z THURSDAY WILL MOVE SLOWLY SWD DURING THE DAY. WITHIN THE SWLY MID-LEVEL FLOW DOWNSTREAM FROM THIS FEATURE…A SHORTWAVE TROUGH OVER THE NRN PLAINS WILL WEAKEN AS IT MOVES ACROSS THE UPPER MIDWEST AND INTO AN AREA OF UPPER LEVEL RIDGING. A COLD FRONT WILL MOVE E ACROSS THE NRN PLAINS AND EXTEND FROM ERN MN SWWD TO A SFC LOW VCTY SWRN KS BY 00Z FRI. A DRYLINE WILL EXTEND SWD FROM THE SFC LOW INTO W TX. AN AREA OF SFC LOW PRESSURE DEVELOPING OFF THE SOUTHEAST U.S. COAST WILL MOVE NWD THURSDAY. CONSULT THE SPECIAL TROPICAL WEATHER OUTLOOK ISSUED BY THE NATIONAL HURRICANE CENTER FOR THE LATEST INFORMATION. TSTMS WILL LIKELY BE ONGOING AT 12Z THURSDAY IN AT LEAST TWO AREAS…FIRST ACROSS ERN NEB/WRN IA IN ASSOCIATION WITH THE NEWD-MOVING SHORTWAVE TROUGH…AND A SECOND AREA ACROSS SRN OK/RED RIVER AREA SUPPORTED BY LOW-LEVEL WAA. …CENTRAL/SRN PLAINS… IN THE WAKE OF MORNING TSTMS…HEATING/DESTABILIZATION IS LIKELY TO OCCUR IN ADVANCE OF THE COLD FRONT AND DRYLINE…RESULTING IN MODERATE-STRONG SFC-BASED BUOYANCY BY LATE AFTN. LITTLE IN THE WAY OF LARGE-SCALE FORCING FOR ASCENT IS EVIDENT THURSDAY…AND THE TIMING OF SUBTLE SPEED MAXIMA WITHIN THE BROAD SWLY UPPER LEVEL FLOW WILL LIKELY PLAY A ROLE IN EVENTUAL TSTM DEVELOPMENT. FURTHER…A BRIEF PERIOD OF SHORTWAVE RIDGING IN THE WAKE OF THE NRN PLAINS IMPULSE MAY DELAY INITIATION ACROSS THE CENTRAL PLAINS UNTIL LATE IN THE DAY. BY LATE AFTN/EARLY EVENING…TSTMS ARE LIKELY TO DEVELOP NEAR THE TRIPLE POINT ACROSS SWRN KS…AND ALSO ALONG THE TX PANHANDLE/S PLAINS PORTION OF THE DRYLINE. STRENGTHENING WIND FIELDS WILL RESULT IN DEEP-LAYER SHEAR SUPPORTIVE OF SUPERCELLS…AND A PLUME OF STEEPER MID-LEVEL LAPSE RATES WILL BECOME REESTABLISHED AND ADVECT EWD ACROSS THE AREA. LARGE HAIL AND SOME TORNADO RISK WILL EXIST WITH INITIALLY DISCRETE CELLS…WITH TSTMS COALESCING INTO AN MCS DURING THE OVERNIGHT HOURS AS A NOCTURNALLY-STRENGTHENING LOW-LEVEL JET/WAA DEVELOPS. INTRODUCTION OF A SIG HAIL AREA MAY BE NEEDED IN LATER OUTLOOKS AS SPATIAL UNCERTAINTY DIMINISHES. …IA/NWRN MO… DESPITE WIDESPREAD CLOUDS/PRECIP…THE PRESENCE OF LOWER-MID 60S DEW POINTS AND SOME DIURNAL HEATING SHOULD RESULT IN MODERATE SFC-BASED BUOYANCY AHEAD OF THE COLD FRONT. DEEP-LAYER SHEAR WILL BE SUBSTANTIALLY WEAKER THAN FARTHER SOUTH…BUT SUFFICIENT FOR MULTICELL TSTMS WITH A RISK FOR ISOLATED SEVERE HAIL/WIND DURING THE AFTN/EVENING. …SRN NORTH CAROLINA COAST AFT 06Z… 00Z GUIDANCE DEPICTS STRENGTHENING LOW-LEVEL WIND FIELDS ASSOCIATED WITH THE DEVELOPING SFC LOW OFF THE SERN U.S. LATE IN THE PERIOD. RESULTING HODOGRAPHS SHOW SUBSTANTIAL LOW-LEVEL CURVATURE AND WOULD SUPPORT SOME TORNADO RISK WITH ANY STRONGER CELLS APPROACHING THE COAST. GIVEN TIMING UNCERTAINTIES WILL NOT INTRODUCE SVR PROBS WITH THIS OUTLOOK.
Severe Threat Friday
…SUMMARY… SEVERE THUNDERSTORMS WILL BE POSSIBLE FRIDAY ACROSS PORTIONS OF THE CENTRAL AND SOUTHERN PLAINS NORTHEAST INTO SOUTHWEST ILLINOIS. …SYNOPSIS… AN UPPER LOW OVER SRN CA WILL MOVE EWD TO CENTRAL AZ DURING FRIDAY AS A BELT OF SWLY FLOW ALOFT PREVAILS FROM THE SRN/CENTRAL PLAINS INTO THE GREAT LAKES. A FRONTAL BOUNDARY WILL EXTEND FROM THE MICHIGAN UPPER PENINSULA SWWD TO THE NRN TX PANHANDLE LATE FRIDAY AFTN WITH A DRYLINE EXTENDING SWD THROUGH THE TX PANHANDLE/W TX. A SFC LOW SOUTH OF THE NORTH CAROLINA COAST WILL MOVE NWD. CONSULT THE LATEST INFORMATION FROM THE NATIONAL HURRICANE CENTER. …SRN/CENTRAL PLAINS… A CONVECTIVE COMPLEX MAY BE ONGOING FRIDAY MORNING ACROSS PORTIONS OF KS/OK AIDED BY WAA ASSOCIATED WITH A SWLY LOW-LEVEL JET. RESIDUAL OUTFLOW/CLOUDS WILL INFLUENCE THE EFFECTIVE FRONTAL POSITION AND SUBSEQUENT PREFERRED LOCATIONS FOR NEW TSTM DEVELOPMENT. HEIGHT FALLS/LARGE-SCALE FORCING FOR ASCENT ASSOCIATED WITH THE EWD-MOVING UPPER LOW WILL REMAIN W OF THE CENTRAL/SRN PLAINS FRIDAY…HOWEVER LOW-AMPLITUDE IMPULSES WITHIN THE SWLY FLOW WILL ONCE AGAIN INFLUENCE AFTN/EVENING CONVECTIVE TRENDS. ONE IMPULSE TRAVERSING THE CENTRAL PLAINS EARLY FRIDAY MAY AID THE CONTINUATION OF MORNING TSTMS THROUGH THE AFTN ACROSS PORTIONS OF MO/IL. THE FOCUS FOR MORE CONSEQUENTIAL TSTM DEVELOPMENT FRI AFTN WILL BE ALONG THE FRONTAL BOUNDARY AND SWD ALONG THE DRYLINE OVER SRN KS/OK/W TX. STG SFC-BASED BUOYANCY…40-50 KTS OF DEEP-LAYER SHEAR AND STEEP MID-LEVEL LAPSE RATES WILL INITIALLY FAVOR SUPERCELLS WITH LARGE HAIL. RELATIVELY LOW LCL HEIGHTS AND NOCTURNALLY INCREASING LOW-LEVEL FLOW WILL ALSO RESULT IN A TORNADO THREAT DURING THE EVENING HOURS BEFORE UPSCALE GROWTH INTO A MESOSCALE CONVECTIVE COMPLEX OCCURS. DAMAGING WINDS AND LARGE HAIL WILL REMAIN POSSIBLE AS THE MCS MOVES EWD OVERNIGHT. …SRN NC COAST… LATEST GUIDANCE PLACES A SFC LOW ALONG THE COAST NEAR THE NC-SC BORDER DURING THE DAY FRIDAY…WITH STRONG LOW-LEVEL ELY FLOW RESULTING IN SUBSTANTIALLY-CURVED LOW-LEVEL HODOGRAPHS. THE RISK FOR A TORNADO WILL EXIST WITH CONVECTIVE CELLS NEAR/ALONG THE COAST.
Severe Threat Saturday
…DISCUSSION… THE UPPER LEVEL LOW NEAR THE FOUR CORNERS REGION AT 12Z SAT WILL LIFT NEWD TOWARDS THE UPPER MIDWEST/GREAT LAKES REGION TUESDAY…INTERACTING WITH A NRN-STREAM UPPER TROUGH DIGGING SEWD FROM MANITOBA AS IT SHIFTS INTO THE NERN U.S. BY WED. A WEAKER BELT OF WLY FLOW ALOFT WILL PERSIST FROM TX ACROSS THE GULF COAST. …SATURDAY/D4… DESPITE ANOTHER ROUND OF MORNING TSTMS OVER PORTIONS OF THE CENTRAL/SRN PLAINS EARLY SAT…THE INGREDIENTS APPEAR TO BE COMING TOGETHER FOR A SUBSTANTIAL SEVERE WEATHER EVENT ACROSS THE SRN/CENTRAL PLAINS SAT AFTN/EVENING. ALTHOUGH SOME TIMING/LOCATION DIFFERENCES EXIST AMONGST LATEST GUIDANCE…THERE IS GENERAL AGREEMENT ON HEIGHT FALLS/DCVA OVERSPREADING A VERY MOIST WARM SECTOR /SFC DEW POINTS 65 TO NEAR 70/ AHEAD OF A DRYLINE EXTENDING FROM SWRN KS SWD INTO W TX. 50-60 KTS OF SWLY 500 MB FLOW WILL ROTATE AROUND THE UPPER LOW AND ACROSS OK/KS AS A SFC LOW TAKES SHAPE OVER SWRN KS BY EARLY EVENING. SVR TSTMS WILL LIKELY DEVELOP ALONG THE DRYLINE AND NEAR THE SFC LOW/WARM FRONT DURING THE AFTN IN AN ENVIRONMENT FAVORABLE FOR SUPERCELLS WITH ALL SEVERE HAZARDS POSSIBLE. STORMS SHOULD EVENTUALLY EVOLVE INTO CLUSTERS OR LINES WITH A CONTINUED SVR THREAT OVERNIGHT.
Severe Threat Sunday
…SUNDAY… AS THE SFC LOW LIFTS NEWD TO NR THE NEB/IA BORDER…SVR TSTMS APPEAR POSSIBLE ONCE AGAIN IN ADVANCE OF A COLD FRONT EXTENDING SWD FROM THE LOW INTO ERN OK/N TX…AND NEAR/SOUTH OF A WARM FRONT EXTENDING EWD ACROSS CENTRAL/NRN IL. A PLUME OF STEEPER MID-LEVEL LAPSE RATES MAY BE IN PLACE SUPPORTING MODERATE-STRONG BUOYANCY AS HEIGHT FALLS/FORCING FOR ASCENT SHIFTS EWD ACROSS THE AREA. A MIX OF STORM MODES INCLUDING SUPERCELLS AND LINES/CLUSTERS APPEARS PROBABLE.
3 Day Precipitation Outlook
The area of low pressure lifting northeast into the Upper Midwest through the end of the week will be responsible for some heavier rainfall tallies across parts of the Central and Southern Plains through the early weekend timeframe. While folks in the Upper Midwest aren’t expecting as much as areas in the south, this is still welcomed as many areas are dealing with drought there.
7 Day Precipitation Outlook
When it rains, it pours! Another area of low pressure will develop late week/weekend and bring even more rain and thunder across the Central and Southern Plains. Note that according to NOAA’s HPC, the 7 day precipitation forecast suggests nearly 2″ to 4″+ in those areas. Interestingly, some of the moisture across the higher elevations in the Rockies could be in the form of heavier snowfall! Also note the bullseye of heavy moisture just off the Carolina Coast in association with our interesting low pressure system there.
Extended Temperature Outlook
Those who are enjoying the mild weather as of late may enjoy the forecast below! According to NOAA’s CPC, the 8 to 14 day temperature outlook suggests above average temperatures returning for mid May (May 13th – 19th)! There will be a brief cool down before then, but it should only last a few days.
May 5th X-Flare
“The sun is no longer quiet. Emerging sunspot AR2339 unleashed an intense X2-class solar flare on May 5th at 22:11 UT. NASA’s Solar Dynamics Observatory captured the extreme ultraviolet flash:”
“A pulse of UV radiation and X-rays from the flare caused a strong radio blackout over the Pacific side of Earth. This map shows the extent of the blackout, which affected frequencies below 20 MHz. Mariners, aviators, and ham radio operators are the type of people who might have noticed the disturbance.
The explosion also hurled a CME into space: movie. Traveling faster than 1100 km/s (2.5 million mph), the expanding cloud does not appear to be heading for Earth.”
Thanks for checking in and have a great rest of your week! Don’t forget to follow me on Twitter @TNelsonWX