AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE TALLAHASSEE FL 842 PM EST Wed Dec 28 2011 Updated most recently for SYNOPSIS and Near Term sections. .SYNOPSIS...A fairly potent MID-upper level SHORTWAVE TROUGH was moving quickly east-southeast this evening through east Texas. Ahead of the approaching wave, higher clouds were streaming into the eastern Gulf Coast region. The lower levels of the ATMOSPHERE across the region were very dry, though, AS sampled by the 00z soundings. A weak surface HIGH PRESSURE was centered almost directly on the forecast area with very light winds. Some west- southwesterly return FLOW was beginning across parts of southern Louisiana and Mississippi on the back side of the high, but deeper LOW-level MOISTURE had not made any progress inland in those areas. Therefore, despite relatively strong forcing for vertical motion ahead of the approaching wave, limited moisture and weak WIND fields underneath the low-level high pressure are expected to keep RAIN chances generally under wraps in the short term. && .NEAR TERM (Tonight)...Most of the near-term grid edits this evening were focused around TEMPERATURE trends tonight, and then POPS over the Gulf waters over the next 24 hours. As mentioned in the "Synopsis" section, there is a potent PV ANOMALY moving into southwest Louisiana at the moment. Objectively analyzed dynamic TROPOPAUSE maps suggest that the 1.5 PVU surface could be as low as 550-600mb with that wave. Therefore, it`s not surprising that there is a decent amount of forcing for ascent (especially in the middle and upper TROPOSPHERE) ahead of the wave. This is resulting in some CIRROSTRATUS pushing in from the west, and IR satellite suggests this could be fairly thick in spots. Therefore, the radiational cooling process could be limited by the increased CLOUD cover overnight. Low temperatures were kept fairly close to the previous forecast, but FROST wording was toned down, and the mention of freezing temperatures was removed from the HWO. Changes to PoPs were made into Thursday, as high resolution model guidance is insistent on SCATTERED showers developing late tonight and then pivoting into the western sections of our coastal waters tomorrow. These showers develop near a subtle surface trough from near Mobile Bay south into the Gulf, and in an area of increasing low-level moisture. Indeed, there appears to be some low clouds (4000 FT ceilings) offshore of Mobile Bay stretching south into the NC Gulf of Mexico. Some of the PoPs derived from high-res guidance was as high as the upper "CHANCE" RANGE (40-50%), but we opted to trend things up from a dry forecast to "Slight Chance" PoPs (20%) for now. With models keeping most of the SHOWER activity offshore, we kept rain chances over the water as well. && .SHORT TERM (Thursday through Friday NIGHT)...Moving ahead to Friday, several models hint at some moisture returning and even some very light showers moving into the western Florida zones from the Gulf. The 00z NAM was quite bullish and showed 30 to 50 PoPs over portions of the panhandle. The 12z NAM backed off somewhat and shows 20 to 30 PoPs. This seems overdone and have instead just gone with a silent 10 POP for now and will wait for some more model consistency before adding mentionable PoPs into the forecast in that area on Friday. The pattern just does not look too favorable for precip, and there is no real well defined upper level shortwave forecast for Friday in that area. Temperatures are expected to commence a slow warming trend through the short term after tonight with highs near 70 LIKELY by Friday. .LONG TERM (Saturday through next Wednesday)...The period will start our dry and mild through the weekend with surface high pressure to our east and near zonal flow aloft. MIN TEMPS will be in the mid to upper 40s with highs in the lower 70s across most of the forecast area. Prior runs of the GFS and ECMWF (Euro) showed big differences in their handling of the next trough to amplify into the east. While the GFS remains a bit more progressive, the Euro has moved sharply toward the GFS and away from its prior solutions of cutting off a huge upper low in the vicinity of the southern Appalachians. This leads to similar timing for the cold frontal passage, which is PROGGED for Sunday night into early Monday. The GFS still shows a dry frontal passage, while the Euro shows a band of frontal PRECIPITATION, which incidentally departs well before it gets cold enough for anything but rain. Since the Euro is trending toward the GFS, we will maintain our CURRENT forecast of a dry frontal passage. However, we do plan on going below the operational guidance for temps by a FEW degrees to account for the fact that MOS tends toward CLIMATOLOGY that far out and the Euro is much deeper with the trough. This all translates into temps taking a tumble behind the cold FRONT. Highs Monday will be near to a couple of degrees below NORMAL. Monday night should see temps well down into the 30s with some areas dipping below freezing. On Tuesday and Wednesday, we are calling for MAX temps in the lower to mid 50s north and mid to upper 50s south. Wednesday morning should see temps a couple of degrees below freezing. Note that if the current Euro solution verifies (with 850-MB temps some 8 to 12 degrees below zero), temps will be significantly colder than currently advertised from Monday night into Wednesday, certainly low enough for the area to see the first WIDESPREAD hard FREEZE of the season. Stay tuned. && .AVIATION (through 00z Friday)...VFR is expected to prevail through the period with some high CIRRUS and light winds. Current satellite analysis and offshore observations are showing a 3500 ft cloud deck over the northwestern Gulf of Mexico. This cloud deck is expected to affect KECP and KDHN during the early morning hours. No significant ceilings are expected however. && .MARINE...As high pressure builds eastward across the Gulf, winds and SEAS are expected to remain light through the weekend. Winds and seas may elevate to ADVISORY levels early next week after the passage of the next cold front. && .FIRE WEATHER...Much cooler and drier AIR is building into the region behind the cold front that passed through the area Tuesday morning. The afternoon relative HUMIDITY is forecast to drop near 35 percent across parts of the Florida big bend and panhandle today, Thursday, and Friday. However, red flag conditions are not expected to occur as durations of low relative humidity are expected to be short.