There are only small differences between the GFS and euro concerning the pattern evolution through mid week.
A strong short wave trough will pass across the Plains tonight and early on Monday. The surface reflection of this system is a very deep cyclone which will track along the South Dakota/Nebraska border toward Southern Minnesota. There are model indications that scattered showers and thunderstorms will form over Central Oklahoma by Monday morning. These will track across Eastern Oklahoma during the morning and early afternoon. Another warm day is in store for the state on Monday before a southward moving cold front crosses Northern Oklahoma from late Monday into early Tuesday.
The front is expected to stall just south of I-40 on Tuesday. Tuesday morning will be chilly across the northern half of the state, while seasonably warm temperatures will be found near and just north of the Red River. By late Tuesday, another strong storm system will be moving toward the Plains. Surface pressures will fall over the High Plains and the front across the state will begin to lift back to the north. There is an outside chance of a thunderstorm or two on Tuesday in the area of a dryline/warm front intersection which is expected to be located over Western Oklahoma.
By Wednesday morning, the front will have lifted to near the Kansas border, leaving most of the state in the warm sector. With another day of return flow, moisture should be sufficient for the atmosphere to become quite unstable through the day. Lifting associated with the approaching Western U.S. system will start to spread across the Plains, and showers and thunderstorms will be possible across the main body of the state. Current indications are that sufficient instability and deep layer shear will be in place to support a severe threat from storms that are able to form. It also appears that all facets of severe weather will be possible – including tornadoes. With this being the first significant severe weather episode this year, now is a good time to review severe weather safety rules.
For years, the rules were fairly simple. Storm shelter is best, otherwise use the center part of the house – lowest level – smallest room. Put as many walls as possible between you and the tornado. Cover up and hang on! Recently, we have been encountering great numbers of people fleeing in vehicles. With that in mind, the following advice is offered: If you are in a building where you don’t feel safe, the time to go to better shelter is when a watch is issued. Do not wait until you are in a warning – it will likely be too late to allow you to reach your safe spot in time. If you find yourself in a warning, take the best shelter that is available to you at your location.
Monday morning: 53
Tuesday morning: 42
Tuesday: 67 / Showers and thunderstorms possible by evening
Wednesday morning: 60 / Showers and thunderstorms possible
Wednesday: 75 / Showers and thunderstorms likely
A strong short wave trough will be advancing eastward across the Central Rockies on Sunday. This will result in a rapidly deepening area of low pressure over Eastern Colorado. The light winds of Saturday will be replaced with steadily increasing winds out of the south on Sunday. Wind gusts over Northwest Oklahoma may approach 50 mph. Most places west of I-35 will see gusts to 40 mph. Humidity will drop to less than 30 percent over most of the western half of the state during the afternoon. The combination of low humidity and strong winds will result in very high fire danger. The high wind gusts will likely continue through the night and into Monday morning.
Moderate southwest flow aloft is spreading northeastward out of Texas, across the Lower Mississippi Valley. By afternoon, a low level jet will extend from Louisiana to Arkansas, and this feature will continue to aid in elevating low level moisture across the threat area. A surface low will be found over Central Texas, and a warm front will extend east northeastward. This warm front will provide the focus for severe thunderstorm development this afternoon. Initial storms are expected from Western Arkansas to Central Texas. These storms will be capable of producing some large hail and damaging winds. With time, longer lived, discrete supercell storms will be capable of producing a couple of tornadoes.
The weather pattern will remain an active one with several short wave troughs embedded in moderately strong west to east flow across the U.S.
A strong short wave will pass across the Plains on Thursday. The surface reflection of this system will be a deep low pressure area that will track across Northern Kansas to the Iowa/Missouri border. A dryline, marking the western edge of the low level moist plume will move to Eastern Oklahoma during the afternoon. This boundary will become a focus for severe thunderstorm development late in the day. Across Central Oklahoma, a warm and dry southwest to northwest wind on Thursday will result in elevated fire danger.
Another short wave will pass across the Plains on Friday. This will result in lowering surface pressures over Northeast Texas, as well as a southward spill of cool air out of Kansas into Oklahoma.
The next system to affect the state will approach the Plains on Sunday. Pressures will fall over the Plains during the day and winds will be quite strong out of the south.
No precipitation is expected across Central Oklahoma through the end of the month.
Thursday morning: 52
Friday morning: 39
Saturday morning: 34
Sunday morning: 45
A strong upper system will move eastward across the Southern and Central Plains on Thursday. At the surface, deep low pressure will organize and move to near the Iowa/Missouri border by mid afternoon. A dryline and cold front will extend southwestward from the low. So far this year, there has not been a robust return of low level moisture from the Gulf of Mexico. While moisture return won’t be significant in advance of this system, it does appear that it will be sufficient enough to support organized severe thunderstorms by mid to late afternoon. Initial development is expected over Northern Missouri with further development southward along the western side of the moist plume into extreme Northeast Texas. Deep layer shear will be sufficient for rotating updrafts. While a couple of tornadoes will be possible with any discrete supercells, the more likely scenario will be line segments containing damaging winds as they push toward eastern sections of Missouri and Arkansas.
Strong southwest winds, warm temperatures and low humidity will result in an area of critical fire danger from Central Oklahoma southwestward into New Mexico.
An upper level storm system will lift northeastward across the state today, generating showers and a few thunderstorms. Thunder will likely be limited to areas along and just north of the Red River. Precipitation amounts are not expected to be excessive, with barely measurable amounts forecast across the Panhandle and near 1/2 inch possible across Southeast Oklahoma. In Okarche, about 1/4 of an inch of rain is expected. Cloud cover and precipitation will keep temperatures cool today with highs only expected to reach into the 50′s. The temperature should actually warm as we approach Midnight tonight after precipitation has moved out of the area.
Winds will be quite gusty across Central and Western Oklahoma today, with south winds reaching to between 35 and 45 mph.
My favoritism for spring is heavily driven by the return of gulf moisture and the return of thunderstorms to the forecast. But a close second to storms is the return of garden weather. The early season planting of things like onions and potatoes has already taken place, and now it is time to look for that last freeze which will signal the planting start for tender vegetables.
Repeated freezes last year went well through April and even into May. Our record for the latest last freeze occurred on May 3rd, and that was enough to finish off what little we had remaining after the April freezes.
Model data over the last week has been showing a lot of good news. It appears that the light freezes which have occurred over the past couple of days, and the one that will occur on Tuesday morning (25th), stand the chance at being our last of the season.
For the next couple of weeks, I will be keeping track of forecast morning low temperatures based off of the operational GFS. These forecasts extend out to 16 days, and while usually are not very accurate at that range, can give you an idea which way model trends are headed. Frequently, it’s those trends which can tell you if it is going to be cooler, warmer, dryer, wetter. One thing to keep in mind is that these are exact point forecasts from that model. They are not being used in combination with other model data, or adjusted based off of trends or biases. The bottom line is that they have a chance of being well off base. The data that I am using will come from model data generated at 7 am and 7 pm daily. The model is also generated at 1 pm and 1 am each day, but I will only use the morning and evening runs. A temperature posted in bold purple indicates a forecast temperature 32 degrees or colder. Highlighted blocks of red show a forecast that has trended warmer, and a block of blue indicates a forecast that has trended cooler. The chance of last freeze after a date is based off of 78 years of historical data. April 5th is the average last freeze date in Okarche and 49% of the dates of last freeze have occurred after that date since 1936.
The running forecast data can be viewed at: http://www.okweatherwatch.com/wx/forecastlast.pdf
A look at all dates of last freeze can be viewed at: http://www.okweatherwatch.com/wx/okarchelastfreeze.jpg
The weather pattern over the next several days is one that we have become used to seeing over the past couple of months. Strong west northwest flow will extend from Western Canada to the Eastern U.S. Embedded short wave troughs will keep cold air spilling southward across the northern and eastern portions of the country. Glancing blows of cold air will keep temperatures slightly below normal on Monday and Tuesday – with morning freezes possible each day. Temperatures on Wednesday will also likely end up below normal, but this will be driven more by cloud cover and precipitation.
A small but fairly strong upper system will be sliding underneath the main flow across the Southwestern U.S., reaching the Plains by Wednesday. Models have trended quicker with this system over the past 24 hours. As it approaches, deep low pressure will organize just northwest of Oklahoma. Winds will become quite strong out of the south on Wednesday and there will be an increase in low and mid level moisture. As warm air advection and moisture increases, showers and a few thunderstorms are expected to develop over Southwest Oklahoma during the morning hours on Wednesday. These will spread northeastward across much of Central and Southeast Oklahoma during the day. Thunder will likely be confined to areas near the Red River. Northwest Oklahoma will see less than 1/10th of an inch of precipitation. Across Central Oklahoma, up to 1/4 inch is possible. Amounts around or slightly more than a 1/2 inch will be possible across South Central and Southeast Oklahoma. Okarche Weather:
Monday morning: 31
Tuesday morning: 28
Wednesday morning: 35
Wednesday: 50 / Showers likely
Strong flow aloft with embedded short wave troughs will move from Western Canada southeastward toward the Great Lakes over the next several days. This will start arctic air moving southward which will reach Oklahoma in a modified form late on Friday and early Saturday. Temperatures above normal on Thursday and Friday will be replaced with cooler than normal temperatures on Saturday and Sunday.
Models have been fairly consistent in developing showers and thunderstorms across the southeast half of the state by early evening on Friday. Showers are likely to persist through much of Saturday over Eastern Oklahoma.
Thursday morning: 36
Friday morning: 48
Saturday morning: 37
Sunday morning: 31
The forecast for the next several days is pretty straight forward. A long wave trough that currently extends from the Great Lakes to South Texas will shift east of Oklahoma during the next 24 hours. A ridge will build over the Plains on Monday, but another strong storm system will be over the Central and Northern Rockies. This system will quickly be moving toward the Plains. By Tuesday afternoon, a closed low will be located near the Iowa/Nebraska border with a strong band of mid level wind surging across the Central and Southern Rockies to the Central and Southern Plains. This strong storm will lift toward the Great Lakes by Wednesday.
At the surface, Monday morning will see the state cool, with fairly light winds. It won’t take long for the winds to increase out of the south in advance of the next system. By Monday afternoon, winds will be quite strong out of the southwest across the northwest 1/2 of the state. This will also lead to a nice afternoon warm up – especially over far Western Oklahoma and the Panhandle.
A cold front will move across the state on Tuesday. This will result in another minor cool down late Tuesday and Wednesday morning.
On Wednesday, high pressure will be shifting southeast, allowing winds to increase slightly out of the south across the Panhandle and much of Western and Northern Oklahoma. Temperatures will rebound to near seasonal normal Wednesday afternoon.
Monday morning: 28
Tuesday morning: 39
Wednesday morning: 33